Antimicrobial products in wound care
Antimicrobial products in wound care are a hot topic. With increased focus on antibiotic resistance, we turn more often to antimicrobial products to treat and prevent infections in wounds.
Let us get one thing straight from the start. Most wounds do not need an antimicrobial agent. A common misconception is that using an antimicrobial wound product is always better than using a regular wound product. There are always some bacteria in a wound, often pathogenic bacteria. However, remember that you always have bacteria on your skin, and you usually are not too concerned about them either. We should never try to sterilize a chronic wound. Firstly, you would never succeed- bacteria will keep coming back into the wound continuously. Secondly, it is thought that a good balance of microbes in a wound is actually beneficial to wound healing.
If there is a serious infection, where microbes have entered through the wound into surrounding tissues, we can typically not reach these using topical antimicrobial products. So yes, there are situations where systemic antibiotics are warranted. However, if there are no apparent signs of infection, antibiotics always never are indicated. The level of misuse of antibiotics in wound care is alarming. Many patients with chronic wounds have been prescribed at least one course of antibiotics. We rarely use antibiotics at our clinic, where we deal with severe wounds. To give you some perspective: in less than 5-10% of our patients, we prescribe antibiotics, but almost 70% of the patients referred to us have been given a course of antibiotics by their GP's. Anyhow, this was a digression - in this chapter, we shall focus on antimicrobials and not antibiotics.
The indication for using antimicrobial products in wounds is mainly when we suspect a high bacterial burden. Mostly it is pretty obvious when there are too many bacteria in the wound. We can usually see this by how the exudate looks ( usually slimy exudate) if there is a suspicious smell or signs of inflammation in the peri-wound area. Inflammation alone is, however, not a very good predictor of infection. Many wounds which are not infected can be inflamed nonetheless. Sometimes it can be more challenging to determine whether we have a higher than an optimal concentration of bacteria in the wound. There may just be a hint of a yellowish-greyish slime layer on top of the wound bed, indicating that there may be a biofilm issue in the wound.
Taking a bacterial swab routinely of all chronic wounds is not helpful. It will only give you headaches because you will wonder how to deal with the results. If you do a routine swab from a leg ulcer, you will almost always find a concoction of different pathogenic bacteria. These results tell us very little or nothing. If you take a routine swab of a non-infected pressure ulcer of the sacrum, you will most likely find Staphylococcus aureus, different Enterococci species, E. coli, and maybe some Pseudomonas aeruginosa there living happily in a sort of balance. So what? Need we be worried? Usually, no.
Sometimes we have a situation where there are no apparent signs of infection or increased bacterial burden, but the wound is not progressing as expected. The blood circulation seems adequate, and we have thought about most other factors without any improvement in the wound. In these cases, it may actually be wise to take a bacterial swab to check on the bacteria living in the wound. Especially in cases where we find monocultures of Pseudomonas aeruginosa or Streptococci, this may indicate that the bacteria are inhibiting wound healing. We prefer a happy mix of bacteria where they all compete with each other and, in that way, keep each other under control. When we find monocultures of certain bacteria in a wound, it can mean that these have "hijacked" the wound and expelled all other bacteria. This brings us to another point - trying to eradicate as many bacteria as possible from a wound can harm the positive balance of bacteria and give rise to a monoculture of one strain.
If we think that the bacterial burden is higher than optimal, and there are no apparent signs of severe infection that warrant antibiotics, we should use an antimicrobial agent or dressing. This is where we are challenged by a confusing variety of products and little consensus about the best practice here. Should we use silver-based antimicrobials? What about povidone-iodine? Should we use an antibacterial rinsing solution? Is honey as effective as other antimicrobials? In addition, some myths are circulating about specific products that add to this confusion. We will try to clear up some of this confusion but cannot promise you complete clarity- it is a complex topic.
Let us start by looking at the most commonly used antimicrobials in wound care. While the list contains several exotic-sounding chemical names, some of the other products you have available in your kitchen. While the number of antimicrobial products on the market is enormous, the list of ingredients is not so long. It is not difficult to find something that works against microbes. What is difficult is to find something that inhibits microbes but at the same time isn't harmful to healthy cells.
Polyhexanide ( also known as Polyhexamethylene Biguanide ( PHMB) or Polyaminopropyl Biguanide (PAPB)
Octenilin ( Octenidine dihydrochloride)
Super oxidized water
Iodine based products
Salt ( NaCl)
Vinegar and other products with low pH
Sodium Fusidate ( Fucidin)
Organic dyes - methylene blue, Gentiana violet
Lactic acid bacteria (yogurt)
Wound cleansers with antimicrobial properties
Home -made hypertonic salt water solution
Studies show that salt concentrations equivalent to seawater ( about 3,5%) have an antibacterial effect while not causing harm to healthy cells. To make this, you add 35 grams salt to 1 Litre of boiled water. As with most rinse solutions, the antibacterial effect is not long-lasting.
Wound wash containing zinc
Zinc has antimicrobial activity. It has been added to mouth rinses and toothpaste to control dental plaque, inhibit calculus formation and reduce halitosis. It is considered a bacteriostatic agent rather than a bactericidal. Interestingly, the bacterial inhibiting effect appears to persist for several hours after application. Several producers have wound washes that contain zinc as the main active ingredient. Examples are 3M Wound Cleanser and CVS Zinc Wound Wash. We have not tried these ourselves but like using zinc because it also has anti-inflammatory properties and several physiological processes going on in a wound like zinc. In effect, when using zinc, we not only inhibit bacteria but also supply the wound with something helpful in wound healing.
Home-made 1% -2%vinegar rinse solution
The literature suggests that 1%- 2% vinegar is an effective antimicrobial rinsing agent. It has the advantage that it also lowers the pH of the wound ( temporarily), which is beneficial to the wound healing processes. Like most antimicrobial solutions, the antibacterial effect is short-lasting, and an antibacterial dressing should be used if you suspect a high bacterial load in the wound. You can use regular clear household vinegar to make this. This type of vinegar is often sold at around 5- 7%, and you have to dilute it accordingly with boiled water that has cooled down.
Acetate buffer ( sodium acetate buffer)
Some clinics use standardized vinegar solutions which are prepared by pharmaceutical standards. These solutions contain vinegar and vinegar salts ( often sodium-acetate) to give the solution buffering properties. By buffering a vinegar solution, it not only has a predictable pH value ( often pH 4 is used for wound care purposes), but it is thought that the pH can remain more stable when the solution comes into contact with wound exudate. In theory, regular vinegar may be neutralized within shorter periods when it comes into contact with wound exudate. Whether the theoretical advantage of buffered acetic acid really makes a difference in a wound is unknown. Most studies on vinegar in wounds have been done with regular vinegar. However, if acetic acetate buffer is available at your clinic, using this instead of ordinary household vinegar makes sense.
Vinegar and Surfactant Wound Wash
This type of wound wash combines the biofilm disrupting properties of a surfactant with vinegar's antimicrobial and pH regulating properties. There are surprisingly few products like this available. One such product is Optima pH Skin Wash, manufactured in Norway and is mainly distributed in Scandinavia. Ideally, it should be applied on a soft brush or a debridement cloth with which the wound is cleansed. We have not found any documentation about the properties of this type of product.
Solutions with PHMB
Polyhexethylene biguanide (PHMB), also known as polyhexanide, is used in many antibacterial wound cleansing solutions. PHMB is a broad-spectrum antimicrobial effective against various pathogens, including Staphylococcus aureus, Pseudomonas aeroginosa, and other bacteria. Some solutions contain only PHMB as the active ingredients, while others also include a surfactant- see the next group below. There are several producers of PHMB based was solutions. The image on the left shows Biakos Antimicrobial Skin and Wound Cleanser by Sanara MedTech.
In our experience, this type of wound cleanser is not strong enough if you have a wound with, for example, heavy colonization with P. aeruginosa. In this scenario, you will need a more potent solution like povidone-iodine or acetic acid.
In recent years there has been a discussion about the safety of PHMB, and high concentrations of PHMB may be cancerogenic. However, the amounts of PHMB in these wash solutions are relatively low, and to date, these concentrations are generally accepted as safe.
Solutions with PHMB and Betaine
Prontosan was one of the first products on the market explicitly designed to tackle bacterial biofilms, and it is one of few products with relatively solid documentation.
Prontosan contains PHMB ( the antimicrobial agent) combined with undecylenamidopropyl betaine ( the surfactant). Neither are very aggressive substances and are very well tolerated. As we mentioned earlier, this sort of product works fairly slowly and needs repeated application. Preferably you should use the solution to scrub the wound with a soft brush or a debridement cloth. Alternatively, you can moisten gauze with the solution and let it lie on the wound for 15-120 minutes. The product is also available as a gel which can be used a s a wound filler to provide longer lasting action of the product. In recent years other producers of PHMB + surfactant solutions have appeared on the market - for example Prophase Wound Cleanser.
In our experience this type of wound cleanser is not effective enough if you have a wound with for example heavy colonization with P. aeruginosa. In this type of scenario you will need a stronger solution like povidone- iodine or acetic acid.
Other solutions with a surfactant + antimicrobial agent
The idea of combining a surfactant with an antimicrobial agent makes sense. The surfactant disrupts the surface of a biofilm. The antimicrobial agent inhibits the bacteria in the exudate and those released from the disrupted biofilm.
Octenilin came onto the market a few years ago and challenged the leading position of Prontosan as a biofilm disrupting agent. Like Pronotosan, Octenilin contains a surfactant (Ethylhexyl glycerine) and an antimicrobial agent (Octenidin HCL). From its documentation, it appears that it has similar properties to its competitor Prontosan.
Super oxidised solutions (Hypochlorous Acid)
A super oxidized solution comprises a low concentration of salt (sodium chloride), dissolved in water, into which an electric current is passed. This produces a mixture of charged particles (ions), mostly comprised of hydrogen, oxygen, and chlorine combinations. These ions rearrange to form new compunds like hypochlorous acid and sodium hypochlorite. These substances all have antimicrobial properties, attacking bacteria on various fronts. The antimicrobial effect happens within a few minutes, but again, the effect is not long lasting.
Although super oxidized solutions have very good mirobiocidal properties they are very gentle to healthy tissue and extremely well tolerated. They are also commonly used for irrigation during negative pressure treatments. We do not know much about how effective they are on biofilm. They do not contain any active substances like surfactants.
Superoxidised solution is also known as superoxidised water, anolyte solution, electrolysed water, and oxidative potential water. It is sold as a rinse solution and as a gel as a wound filler. It is cheap and easy to produce and accordingly there are many different brands to choose from.
Today, there is sufficient documentation to show that Povidone-iodine is a safe and highly effective antimicrobial agent. Until a few years ago, there was quite some controversy about this product. Today the product has retaken its position as one of the most valuable antimicrobials solutions we have. In fact, it may be one of the best biofilm disrupting agents we have - especially concerning biofilm from Pseudomonas and staphylococcus aureus. It is usually sold as a 10% solution. If the wound has a heavy bacterial load, you can use it at this strength. Once the wound clears up, we recommend using a diluted concentration for a few more days, like every other antimicrobial solution on this list. If you simply irrigate the wound with PI solution, the antibacterial effect is not long-lasting. To achieve a longer-lasting effect, you can fill the wound with PI gel after the rinse.
We do not recommend using the PI solution as your routine wound wash for every wound. If you are treating a wound which is doing well- why would you want to disturb the bacterial balance in the wound with something as strong as PI? Use it only when you have to deal with severe bacterial contamination.
Wash solutions for intimate hygiene
Intimate wash solutions contain mild surfactants which can have biofilm-disrupting properties. They can be used as a mild soap and applied using a soft brush or a debridement cloth. As a rule of thumb: if it is gentle enough to be used on the vaginal epithelium, it will not cause harm to a wound. Avoid intimate washes that have many unnecessary additives like scents. Choose an intimate wash with low pH. Rinse out the wash solution with clean water afterward.
Sodium Hypochlorite 0,4-0,5%(Dakin`s solution)
Dakin`s solution is an old wound wash solution that has recently seen a revival of its popularity. It is actually diluted bleach. Sodium hypochlorite ( NaOCl) is often used in household bleaches, although in much stronger concentrations. Although Dakin`s solution has shown very good antimicrobial properties, we do not recommend it ourselves because it has an alkaline pH of around 10-11. If we follow the principle that wounds prefer a ph below 7 to heal, using an alkaline rinse solution feels wrong when other reasonable alternatives are available.
Hydrogen peroxide (H2O2)
In many areas of Africa, hydrogen peroxide is still commonly used as a wound rinsing solution. In western countries, however, it is only rarely used today. It is considered cytotoxic, may interfere with cellular homeostasis, and actually delay wound healing. The antibacterial effect of hydrogen peroxide is also considered to be relatively short ( but isn't that the case with most wound cleansers?)
As mentioned in the chapter above, hydrogen peroxide isn't a poison. It was a very popular product only about 15 years ago, and it may not appear so obvious that it has a negative impact on wound healing. We used it extensively many years ago and found it to promote the healing of wounds rather than delay wound healing. However, if studies show that the product is not optimal for wound healing, we should avoid using it as other alternatives are available.
Chlorhexidine is a potent broad-spectrum antimicrobial agent. It is commonly used as a skin disinfectant before surgical procedures. At lower concentrations (0,05%), it has previously been used as a wound cleansing solution. This practice is seen as obsolete today. Chlorhexidine sometimes causes skin irritation, and it is thought to have cytotoxic properties which may delay wound healing. There is no rationale for using this product in open wounds when we have equally potent antimicrobials like povidone-iodine of acetic acid.
Antimicrobial dressings without silver
Figure 1 A choice of antimicrobial dressings which use other technology than silver. All products in the upper row use PHMB as the active ingredient ( from left: Kerlix AMD, Suprasorb X, CelluDress PHMB, Telfa). The products in the bottom row use other technologies. Sorbact ( bottom left) uses a unique formula where microbes are trapped within the dressing fibers. The active substance in these dressings is dialkyl carbamoyl chloride - DAAC. Xeroform ( bottom middle) contains the antimicrobial bismuth tribromophenate. Fucidin ( bottom right) includes an antibiotic substance, and we do not recommend using this in wound care because it can cause resistant bacterial strains.
Antimicrobial dressings with silver
Dressings containing silver are not a homogenous group. There are foam dressings with silver, Hydrofiber- and alginate dressings with silver and gels or pastes that contain silver. It can be challenging to compare silver-based antimicrobials because silver can vary between products. Some contain silver-sulphadiazine or silver nitrate. More modern dressings use technologies that release free silver ions.
Silver has an inhibiting effect on many types of pathogenic bacteria. Indications for its use are wounds with a high bacterial burden. Many recommendations advise silver products to be used for about 3-4 weeks at most. There is some discussion as to whether bacteria can become resistant to silver. While this phenomenon has been shown under laboratory conditions, we have no conclusive signs of silver-resistant bacteria in wounds.
In western countries, there is a definite overuse of silver-impregnated wound dressings. Some healthcare workers routinely use a silver dressing in all wounds to be on " the safe side." This is not the correct approach to wound care. We should only use such products when we have a problem with high bacterial burdens. However, there are situations where we might use such dressings in a prophylactic manner - for example, in more demanding diabetic foot ulcers.
Some dressings coated with silver need to be moistened before application in the wound. Many producers advise moistening the dressings using regular tap water or sterile water, but not 0,9% NaCl. It is thought that salt molecules can bind to silver ions and thus make them less effective. Some producers are not so concerned about this and state that you can also moisten the dressings with 0,9% saline solution. In wound exudate, there is also NaCl, so you could argue that it doesn't matter what you moisten the dressings with.
Wounds International has written an expert working group consensus on the appropriate use of silver dressings in wounds. Click on the image below to get to a link to this document.
Pastes/Gels with silver
Figure 2 A selection of pastes and gels containing silver. These products are easy to apply to the wound bed. They can also be used in sinuses and fistulas. 1&2. Askina Cagitrol by BBraun is probably the best-documented product in this category. It comes in small tubes as well as in a 500g container. 3. Resta Silver Gel 3. Flamazine contains silver sulfadiazine. It is commonly used in burn care. It is readily available in Africa and there is an overuse of this product in wounds that actually do not need an antimicrobial product. 5 Silver Honey is as the name implies a product containing both silver and honey as the active antimicrobial ingredients. We have no experience with this product and do not know if the combination of these two products gives a significant synergistic effect.
Contact layers with silver
Figure 3 A selection of contact layers containing silver. Contact layers are non-adherent and can be made of different substances like polyester or polyamide. Contact layers are soft and conform easily also to uneven wound beds. They can also be used as the inner layer in negative pressure wound therapy. Note that these products can differ significantly in what type of silver is used and at which concentrations. Silverlon ( bottom right) states that their product has the highest concentrations of silver amongst this group. Physiotulle Ag contains silver sulfadiazine ( the same substance as in Flamazine). Acticoat Flex comes in two variants. Acticoat Flex 3 can be kept on the wound for three days and Acticoat Flex 7 for seven days. You will appreciate that it is helpful to research these products before buying them in bulk.
Gelling fiber dressings with silver
Figure 4 A selection of gelling fibers containing silver. The upper box shows fiber dressings based on cellulose technology. The lower box shows fiber dressings based on alginates. Again, as you can see, there is a confusing amount of products to choose from. The products differ in the concentrations of silver they contain, how much they can absorb, and their tensile strength. These types of dressings turn into a gel-like consistency when moistened. If we have a wound with moderate amounts of exudate, we can place the dry dressing into the wound. If we have a low or no exudate wound, we can premoisten the dressing with saline and then apply it to the wound.
Foam dressings with silver
Figure 5 A selection of foam dressings with silver. These dressings differ in absorption properties and the amounts of silver concentrations. Some have adhesive edges and come in various shapes and sizes. Polymem Max ( bottom left) also includes a surfactant that can aid in cleansing a wound.
Activated charcoal dressings with silver
Figure 6 Finally, a product category with limited choices! Activated charcoal dressings with silver are niche products but can be very useful in selected cases. The activated charcoal helps to neutralize odors and binds bacterial toxins, and silver has direct antimicrobial properties. These dressings are mainly used for heavily colonized wounds that have an offensive smell. Vliwaktiv Ag ( left) comes as absorbent pads and a rope that can be packed into deeper wounds.
Dressings with iodine
Iodine is one of the most potent antimicrobials in our toolbox. It has been used as an antiseptic for almost 200 years. Until about the 1950s, so-called elemental iodine was used, usually suspended in alcohol. Not only was this painful upon application, but elemental iodine has also been shown to be cytotoxic to healthy cells when used for prolonged periods. Moreover, allergic reactions were more common, and it could cause permanent staining of the skin.
Since then, a lot has happened, and new and safe iodine formulations have been developed. However, the bad reputation of iodine remained in large parts of the western world, and iodine was almost seen as a niche product. In many other parts of the world, however, particularly in eastern Europe, Africa, and Asia, using gauze soaked in povidone-iodine solution is probably the most common antimicrobial treatment method of wounds there.
In western countries, iodine is slowly reappearing on the wound care market. However, due to the prevailing misconceptions about iodine in these countries, many caregivers are still somewhat skeptical about using this.
Iodine has excellent bactericidal properties against most strains of pathogenic bacteria, including multi-resistant bacteria. It appears that it is also effective in penetrating biofilm. Some studies suggest that iodine is better at penetrating biofilm than silver or PHMB. It is our own opinion ( based on our own experiences) that iodine is one of the most effective products we have to deal with wounds with a high bacterial burden. It seems to clear up heavily colonized wounds quicker than most other wound care products. It is well tolerated and often leads to a quick build-up of healthy-looking granulation tissue.
There are two main combinations of iodine available in wound care products today.
Povidone-iodine: is a combination of polyvinylpyrrolidone ( how could somebody come up with that name? Luckily, we can use the simpler name version "povidone") and elemental iodine. Povidone-iodine was developed in the 60s and is the most common form of iodine used in wound care worldwide. It is usually used in liquid form. When we apply the povidone-iodine into a wound, the iodine is released gradually, providing an antibacterial effect over several hours.
Cadexomer-iodine: is a combination of the polysaccharide dextrin ( a polysaccharide is a type of sugar) and elemental iodine. This preparation made it possible to present iodine in various forms, like dressings or powder. It is thought that cadexomer- iodine may release iodine over a more extended period, thus reducing the need for dressing changes.
Which of these two types of iodine is best? We don't think that there is a simple answer to this. We have not found a definite answer to this through our literature search. From our own experiences, we can say that we believe that povidone-iodine seems to work quicker. When we have a wound with a high bacterial burden, we use povidone-iodine to reduce the bacterial numbers as rapidly as possible. We soak cotton gauze with the PI and apply this directly into the infected wound. It is usually easy to see when you have to replenish the iodine because the dark brown color fades away as the iodine becomes used up. In most cases, the iodine-soaked gauze needs to be changed at least once a day. In most cases, the wound has significantly cleared up within three-four days, and we can go over to another product.
Because povidone-iodine comes as a liquid, it is used to prep the skin before surgical procedures. In diluted form, it is also commonly used to wash over burns in African clinics. Gauze soaked in iodine is frequently used as a post-surgical dressing on the continent. It is cheap and readily available in Africa, and, understandably, it has found widespread use there. However, we find that many caregivers in Africa turn to povidone-iodine dressings more out of habit than actually needing an antibacterial dressing for a particular wound. In other words, we have seen that some clinics routinely use povidone-iodine on all wounds, whether they look infected or not. While this practice is not necessarily harmful, it may not be beneficial either. From our own experiences, we have also seen that povidone-iodine often brings about nice-looking granulation tissue in the start, but epithelialization seems to appear slower when we use this product. We have no documentation for this observation - it is simply something we have observed on many occasions. We, therefore, believe that it is often wise to change from povidone-iodine to another dressing type in the late phases of wound healing.
Povidone-iodine is usually sold as a 10% solution in Africa. Povidone-iodine is safe to use at that concentration, but it is commonly diluted to about 5% when used in wounds. We see that this varies a lot from clinic to clinic in Africa. Some use the solution undiluted. Others meticulously dilute it with exact parts of water and iodine. Others are not exact about this and dilute it with random amounts of water. For rinsing purposes, some dilute the iodine until it has the color of whiskey :). You get our point- there is no consensus here. So what is the correct method to use the povidone-iodine solution? We have done a literature search, and our findings are inconclusive. Some studies even suggest that lower concentrations of iodine may have a better bacteriocidal effect because when the povidone-iodine is dissolved with more water, it releases more free iodine. What we do ourselves is to use 10% ( undiluted) povidone-iodine in heavily infected wounds for a few days until the wound has cleared up. Then we continue with 5% povidone-iodine for a few more days.
Povidone-iodine is also available as gels and non-adherent contact layers or other dressings. Most of these contain 10% povidone-iodine.
Concerning cadexomer-iodine, the release of iodine happens more slowly but in return over a more extended period. We would choose this type of product in less heavily contaminated wounds, where short shift intervals are unnecessary. It is also possible to use povidone-iodine initially to clean up a wound quickly and then use cadexomer iodine for more extended periods. Cadexomer iodine is available as contact layers or in powder form. In Africa, cadexomer-iodine products are usually more expensive than povidone-iodine, which will undoubtedly influence your choice.
Remember that all iodine products release elemental iodine into the wound. This elemental iodine can be absorbed through the wound surface, enter the bloodstream, and affect the thyroid gland. In patients with thyroid disease, this can, in theory, cause complications. This is a rare complication in minor ulcers and short-term use of iodine products. In patients with wounds with large surface areas, for example, extensive burns, the use of iodine-based products can cause toxicity in patients with thyroid disease. The risk of toxicity is increased when there is renal impairment as well. Thyroid disease is not a rarity in Africa. This is another argument for using iodine products only when you have to and not as a routine wound care product for all types of wounds.
Figure 7 Modern iodine products are either based on povidone-iodine ( first two rows) or cadexomer-iodine ( bottom row). Iodine products are available as pads, contact layers, gels, ointments, or powder (only cadexomer iodine). In Africa, iodine is most frequently applied as gauze soaked in povidone-iodine. This works well but needs to be re-applied often. Some of the products shown above release the iodine more slowly and over more extended periods. In this way, we can reduce the dressing shift frequency.
Figure 8 Wounds International has written an informative article - Iodine made easy- about this topic. Click on the image above to get to a pdf- version of this article.
The use of medical honey in wound care has regained increased attention worldwide. With the concerns about antibiotic resistance, honey and other antimicrobial agents are used more often. The use of honey in wound care has a high "acceptance" in patients, probably because it is seen as a gentle and natural treatment.
Medical honey comes in many different variations - as gels, creams, ointments, contact layers, foams, or alginates impregnated with honey. You may ask yourself - is there a big difference between regular honey and medical honey? We will answer that question shortly.
The indication for using honey products in wound care is primarily when we suspect a high bacterial burden in the wound. We can also use it in a prophylactic manner- that is, to prevent bacteria from becoming a burden in the wound. However, honey performs also very well in wounds without any bacterial load. The osmotic- and pH-lowering effect of honey positively stimulates the wound. Honey has, in many ways, all the attributes we are looking for in a wound care product. It is antimicrobial and provides an ideal moist environment with a suitable pH for cells to thrive. It appears to have an anti-inflammatory effect, which can sometimes also lead to a reduction of pain. Honey often also reduces the smell in necrotic wounds. We have recently ( 2021) done an in-vitro trial at our clinic, where we compared the antibacterial effect of honey on three different bacterial strains ( Pseudomonas aeruginosa, staphylococcus aureus, and Enterococcus fecalis). The bacteria were incubated on blood agar plates, and the antibacterial products were tested on these heavily colonized plates. Regarding how long the antibacterial effect lasted, medical honey outperformed all other products ( super-oxidized water, hyaluronic acid- iodine gel, vinegar hydrogel). After three days, only the plates with honey still showed an antibacterial effect. These results are not published yet.
From our own experiences, we see that honey does a good job of initiating and supporting the autolytic debridement processes in many types of wounds. We also use it to "kick-start" a wound where progress has stalled for one reason or another. We have seen wounds where honey has led to rapid improvements and at the same time other wounds where honey has not led to any significant change in the wound. This is the way it is with most other dressings we use. There are no single dressings that perform perfectly every time, and we do not always understand the mechanisms behind this phenomenon.
You can use honey in most wounds. There is little you can do wrong with this product group. Perhaps the most common mistake is to have too long dressing change intervals initially. Especially in the start when using honey products, many wounds will produce more exudate. This is due to the sugar content of honey that draws water from the wound bed. The look of the wound at the first dressing change can deter both the caregiver and the patient when using honey. The honey has usually turned into a grayish liquid, and there may be increased maceration of the wound edges. Instead of giving up on the honey, try changing the dressing more often, for example, daily. Use a barrier product around the skin edges when using honey. You may want to try another secondary dressing to see if that gives you better results. Our point is- when used correctly, honey can outperform many other dressing types.
We generally do not use honey dressing when we have wounds with much exudate, as honey can lead to even more exudate. For this reason, we seldomly use it in venous ulcers because these tend to have a fair amount of exudate. Of course, you can use honey in venous ulcers too, but preferably first after a while, when compression therapy has led to better exudate control.
We know that many studies show that honey can positively affect diabetic foot ulcers. We have had mixed results with honey in diabetic foot ulcers ourselves; sometimes, we have seen severe maceration even when protecting the peri-wound area and increasing dressing change frequency. This is not to say that you should not use honey in diabetic foot ulcers. We are saying that you have to be vigilant when using honey in these patients and perform frequent dressing changes at the start.
Did you know that some patients actually can have a honey allergy? According to a literature search, this is a rare phenomenon. If you suspect that your patient can have an allergic reaction to a honey product, you obviously have to stop using honey products. Where available, the patient should also be referred for dermatological testing (allergy tests) as this can have consequences for what type of wound care products the patient can tolerate. In most settings in Africa, dermatological testing is not a realistic alternative.
How does honey work in a wound?
Because of the high sugar content, honey exerts a strong osmotic effect on cells, which can stimulate healing processes. Since honey also has a high water content, it provides a perfect moist environment ideal for wound healing. This environment is ideal for autolytic processes that help break down necrotic tissues.
Honey has broad-spectrum antimicrobial properties. It inhibits many types of pathogenic bacteria and fungi, protozoans, and even some viruses. When we use honey in a wound in a prophylactic manner, we may reduce the use of antibiotics in wound care.
The primary antimicrobial effect is due to the high sugar concentration in honey. 95-99% of honey is sugar (mainly fructose and glucose). The sugar binds water from the wound, and this lack of "free" water inhibits bacterial growth.
Even though honey tastes sweet, it is actually an acidic product and has a pH of between 3,2-4,5. The low pH also inhibits many types of bacteria and is ideal for stimulating healing processes in the wound.
When honey comes into contact with wound exudate, hydrogen peroxide is produced via an enzymatic reaction (glucose oxidation). Hydrogen peroxide also has an antimicrobial effect. How much hydrogen peroxide is produced varies significantly between different types of honey.
Medical honey versus regular household honey
You may be aware that most types of medical honey are produced from a honey type called Manuka honey. What makes Manuka honey so unique? One thing is that medical honey is sterilized, but is the effect on the wound really better than honey from the highlands in Zimbabwe or Acacia honey from Ghana? Is it safe to use regular household honey in a wound?
Our literature search has not shown a single documented case of wound infection from the use of regular household honey. So yes, it is assumed to be safe to use regular honey in wounds. In theory, however, there can be a risk of infection. It sounds paradoxical, but some pathogenic microbes can survive in honey despite a high antibacterial effect. Contamination can come from the intestinal flora of the bees or their larvae, from pollen, and secondary after the harvesting ( dust, contaminated containers, contact with skin). Most bacteria cannot reproduce in honey, but bacteria and some other microorganisms can make spores and survive in honey in this form. Several bacteria like bacillus-, clostridium-, enterobacter-, e.coli- and Pseudomonas strains can produce such spores. Different types of fungus can also produce spores.
Some studies have shown bacteria like Clostridium ramosum and Staphylococcus warneri in regular household honey. These bacteria could, in theory, colonize a wound and cause an infection. Again, the chances of this happening are probably minimal.
As you probably know, honey may contain spores from Clostridium botulinum. Therefore, it is an international recommendation that honey should not be given to children as food before they are at least one year of age. It does not help to "sterilize" the honey by heating it. Firstly, the spores of most bacteria can withstand high temperatures. In addition, the heat will destroy the beneficial properties of the honey, which makes it attractive for use in wound care. For this reason, medical honey is sterilized using gamma radiation.
What about the antimicrobial effect of honey? Are there any differences between different types of honey? We have to admit that we thought some years ago that honey is equivalent to honey, i.e., that any differences were probably not significant. We were wrong. Depending on the bees' environment, honey can vary quite a lot concerning sugar content, pH, how much hydrogen peroxide it produces in the wound, and whether it contains other antimicrobial substances. Unfortunately, many studies on honey are paid for by companies producing medical honey, so we have to interpret the results with care. But even independent studies have shown some differences concerning the antimicrobial effect of various types of honey. Whether these differences translate into significant differences in an actual wound is uncertain. In a Norwegian study ( Merckol, 2009), the antibacterial effects of sterile medical honey from New Zealand and Norwegian Woodland Honey were compared. Both types of honey had comparable antibacterial properties, including methicillin-resistant staphylococcal strains (MRSA).
What is all the hype about Manuka honey? Without a doubt, honey derived from the pollen of certain plants contains substances that have antimicrobial properties on their own. In this way, they may give a synergistic effect to honeys own antimicrobial properties. Manuka honey is derived from the Manuka plant ( Leptospermum scoparium). It grows as a bush or little tree on the east coast of Australia, in New Zealand and Tasmania. The plant is used to make an essential oil with antibacterial properties. This oil is sometimes referred to as tea-tree oil. However, the true tea-tree oil is usually derived from another member of the myrtle family of shrubs (this was a digression to get our facts right).
It wasn't until around the '90s that manuka honey started to be marketed as a wound care product. A lot has happened since then. Advertisement- and marketing campaigns have been, without a doubt, successful, and manuka honey has dominated the medical honey market ever since. Manuka honey is also sold as regular food honey, sometimes at inflated prices. Yes, Manuka honey has some properties which differentiate it from other types of honey. Is the hype about Manuka honey justified? Probably not. One of the substances isolated in Manuka honey is called methylglyoxal. This substance is seen as crucial for the long-lasting antimicrobial effect of Manuka honey. Methylglyoxal can be found in most types of honey but usually in lower concentrations. Interestingly, methylglyoxal levels actually are not very high in fresh Manuka honey. Only when Manuka honey is stored for some time at around 37 °C does the amount of methylglyoxal increase. There are probably other types of honey worldwide that also have excellent antibacterial properties and high concentrations of methylglyoxal, but most types of honey have not been appropriately studied. We have noticed that several companies now aim to compete for the honey market in wound care and are starting to perform studies on other honey worldwide. However, Manuka honey remains the medical-grade honey that has the most documentation.
There is no doubt that honey can be an excellent alternative to other dressings in wound care. Honey is used as traditional medicine in wound care in many countries worldwide. Even if most types of food-grade honey do not have any documentation about their individual antimicrobial properties, we can assume that they all inhibit bacteria to some degree and that the stimulating effect of wounds is similar to medical-grade honey.
Medical honey is expensive, and in most areas of Africa, it is not a realistic alternative because of the price. Therefore regular household honey is used here. Since there is no documentation that regular food-grade honey poses any real threat of infection, we can recommend this practice as long as there are no other alternatives. However, it is advised that honey for wound care is purchased in shops instead of from local gatherers. We are concerned that honey produced by individuals can be stored in contaminated containers. In most African countries, beekeepers selling to shops are usually registered and adhere to specific hygiene regulations.
In the western world, however, things are more complicated. For example, there are rigid regulations on what products can be used in the public health sector. Also, honey products must be registered to be used in wound care, and formally only medical-grade honey is accepted. For instance, we cannot use food-grade honey in wound care at our clinic. However, the patient can use food-grade honey if they wish to do so. In this situation, we are obliged to inform the patient that regular honey is non-sterile and that theoretically, spores could be transferred into the wound and that the patient does this at their own risk.
The following are general recommendations for the use of honey in wounds:
Honey is contraindicated when the patient has a known honey allergy
Rarely some patients may feel a stinging sensation when honey is applied to a wound. This is usually only temporary and passes after about half an hour.
Honey paste or cream is applied directly into the wound and covered with a secondary dressing. Often polyurethane foam dressing is used for this. If there is more exudate, a superabsorbent dressing may be appropriate. If you have few resources, regular cotton pads may have to be used as a secondary dressing. Be aware that these may absorb more of the honey and that honey may have to be applied more often.
Use appropriate barrier products to protect the peri-wound area from maceration.
We recommend changing the dressing once daily at the start, sometimes several times daily if there is much exudate. In the course of the treatment, the amount of exudate usually decreases, and longer shift intervals can be used, sometimes as long as five days.
Usually, within about 14 days, we expect to see a definite improvement in the wound. During the first week, the wound is typically busy cleaning up, and after that, granulation slowly sets in. Of course, this is a generalization and will depend significantly on what type of wound we are dealing with.
Honey is not a substitute for sharp debridement when there is much necrosis or signs of severe infection.
Figure 1 The range of medical honey for wound care has become quite diverse and confusing. Contact layers impregnated with honey, foams with honey, and alginates with honey. Some products contain 100% honey; others may contain, for example, only 30% honey. Some contain a mixture of honey and, for instance, cod-liver oil. If you are new to medical honey in wound care, we advise you to start using products containing 100% honey in a tube.