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Honey in wound care: properties and treatment

Rose Cooper
BSc PhD PGCE
Principal Lecturer in Microbiology
Centre for Biomedical Sciences
School of Applied Sciences University of Wales Institute Cardiff

Honey is a sweet, sticky substance that has been important to humans for at least 6,000 years. The earliest documentary evidence of its application in treating wounds dates from approximately 2000 BC when it was used in a recipe for a salve (ointment) for ulcers.(1) It is evident that the ancient Egyptians, Greeks and Romans each utilised honey, as did ancient Indian and Chinese civilisations. Honey was still being used in Britain in the treatment of some wounds until the 1970s. After that it fell into disuse. However, new wound care products based on honey have recently become available, and honey is currently enjoying a revival.

The wound healing properties of honey
Honey is reputed to benefit wounds because of its antimicrobial properties that limit infections and its immunomodulatory properties that promote rapid wound healing.(2) The antimicrobial properties of honey are based on its chemical composition.(3) It is a supersaturated solution of sugars (fructose, glucose, maltose and sucrose) with low water content (Aw 0.6) and slight acidity (pH 3.5-5). All microorganisms require water for growth (Aw >0.85), and most require a pH close to 7. The low availability of water molecules is sufficient to prevent the growth of microorganisms; additionally, few microbial species tolerate a pH below 5.
When honey is applied topically to wounds it exerts an osmotic pressure that promotes exudation that dilutes the honey and increases the availability of water molecules. Yet paradoxically it has been known since 1919 that the antibacterial activity of some honeys increases on dilution. This is due to the generation of hydrogen peroxide by the action of a bee enzyme, glucose oxidase, on glucose.(3) For clinical use it is important to select honey with potency above an equivalent of 10% (w/v) phenol.

Laboratory evidence for the efficacy of honey
A wide range of bacteria are inhibited by honey, but the data that have been published in various studies have been inconsistent, probably because differing honeys and methodologies were utilised.(3) However, testing the effectiveness of a hydrogen peroxide-generating honey of median potency and a nonperoxide honey of median potency against cultures of bacteria isolated from wounds has demonstrated that staphylococci are the most sensitive bacteria,(4-6) and that antibiotic-resistant strains such as methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE) are just as susceptible to honey as their respective antibiotic-sensitive strains.(4,6) By comparing the effectiveness of an artificial honey solution with that of honeys with median potency, it has been shown that bacterial inhibition is not restricted to osmotic effects and that the natural honeys were between three and 10 times more effective depending on the bacterium tested.(6,7) Furthermore the inhibition was due to a killing effect rather than simply interrupting growth.(7) The mechanisms of bacterial inhibition are being further investigated in an attempt to explain the precise cellular locations affected and molecular events involved.
The evidence to support the role of honey in stimulating rapid wound healing is accumulating. Exposure of monocytic cells to sterile honey solutions demonstrated the spontaneous release of proinflammatory cytokines as an indication of cell activation,(8) whereas artificial honey solution had no effect. This is preliminary evidence that honey can modulate the activity of cells intimately involved in the healing process. Another study has indicated that glucose enhanced the growth of dermal fibroblasts in vitro.(9) Since glucose levels in exudates collected from chronic wounds are low,(10) and honey contains approximately 33.5% glucose, it is possible that topical application of honey to chronic wounds promotes local cell growth.

Clinical evidence that honey stimulates wound healing
Although some of the evidence for the efficacy of honey in wound healing comes from animal models, most of it is found in published clinical studies derived from over 500 patients. This has recently been reviewed.(2,11,12) Much anecdotal evidence also exists. Case studies have often involved situations where conventional therapies failed and honey was used as a last resort. Randomised clinical trials to date have mainly involved patients with acute wounds, such as burns or surgical wounds, and the quality of these studies has been criticised.(13) Nevertheless, judging from the increasing frequency of clinical reports within the last few months, there is growing interest in honey for the management of chronic wounds.(14-17)

Conclusion
The clinical use of raw honey obtained from supermarkets or farm outlets is unwise because of the risk of introducing bacterial spores that cause wound botulism. However, the collection of honey by documented routes, its processing under quality-assured pathways and its sterilisation by gamma irradiation before distribution is providing more standardised wound care products. In Australia, Canada and within the EU, increasing numbers and variety of wound care products containing honey that are approved by regulatory authorities are being introduced. In Britain, for example, a manuka honey-impregnated dressing became available on drug tariff on 1 March 2004, and many similar products are now under development.
Previously, healthcare practitioners were justifiably reluctant to utilise unregistered products, but medical opinion is changing, and honey will soon be thoroughly evaluated for the management of wounds. It is important to remember that there are many obstacles to effective healing and that no wound care product has ever been the ideal remedy for all types of wounds and patients. Honey is unlikely to be a panacea solution. The development of modern products containing honey for the treatment of wounds will provide the opportunity for the evaluation of honey in the clinical environment. Further research into the mechanisms that influence healing, and the effects of different floral types of honey on these processes, is ongoing.

References

  1. Jones R. Honey and healing through the ages. In: Munn P, Jones R, editors. Honey and healing. Cardiff: International Bee Research Association; 2001. p. 1-4.
  2. Molan PC. The role of honey in the management of wounds. Wound Care 1999;8:415-8.
  3. Molan PC. The antibacterial activity of honey 1. The nature of the antibacterial activity. Bee World 1992;73:57-70.
  4. Cooper RA, et al. Antibacterial activity of honey against strains of Staphylococcus aureus from infected wounds. J R Soc Med 1999;92:283-5.
  5. Cooper RA, Molan PC. The use of honey as an antiseptic in managing Pseudomonas infection. Wound Care 1999;4:161-4.
  6. Cooper RA, et al. Honey and Gram positive bacteria of clinical significance. Appl Micro 2002;93:857-63.
  7. Cooper RA, et al. The efficacy of honey in inhibiting Pseudomonas aeruginosa from infected burns. Burns Care Rehab 2002;28:366-70.
  8. Tonks AJ, et al. Honey stimulates inflammatory cytokine ­production from ­monocytes. Cytokine 2003;21:242-7.
  9. Han J, et al. Effect of glucose concentration on the growth of fibroblasts in vitro. Wound Care 2004;13:150-3.
  10. Trengove NJ, et al. Biochemical analysis of wound fluid from non-healing and healing chronic leg ulcers. Wound Rep Regen 1996;4:234-9.
  11. Molan PC. A brief review of honey as a clinical dressing. Primary Intention 1998;6(4):148-58.
  12. Molan PC. Clinical usage of honey as a wound dressing:an update. Wound Care 2004;13:353-7.
  13. Moore OA, et al. Systematic review of the use of honey as a wound dressing. Complement Alternative Med 2000;1:2.
  14. Dunford CE, Hanano R. Acceptability to patients of a honey dressing for non-healing venous leg ulcers. Wound Care 2004;13:193-7.
  15. Robson V. Use of Leptospermum honey in chronic wound management. Community Nurs 2004;18(9):24-8.
  16. Stephen-Haynes J. Evaluation of a honey-impregnated tulle dressing in primary care. Br J Community Nurs 2004;9 Suppl:S21-7.
  17. Schumacher HHA. Use of medical honey in patients with chronic venous leg ulcers after split-skin grafting. Wound Care 2004;13(10):451-2.

Resources
US National Honey Board
W:www.nhb.org
Waikato Honey Research Unit
W:http://honey.bio.waikato.ac.nz

Further reading
Honey: a modern wound ­management ­product
Edited by White R, Molan P, Cooper R.
This book by Wounds UK will be published in May 2005