The modern understanding of moisture in wound healing has been influenced by the research carried out by George Winter in 1962. [1] He demonstrated that the rate of epithelialization was almost double in moist wounds covered with polythene. Before his research, there was no conclusive evidence that favored the use of moist dressings in wound care. Traditional dressings that were available tended to dry out wound exudate which delays wound healing. As a result of Winter's pioneering research, several dressings were developed in the coming years that optimized the moisture in the wound microenvironment. 

Importance of Moisture In Wound Healing

A moist wound environment is now regarded as critical in optimal wound healing. Podiatrists and wound care specialists strive to optimize the moisture in the wound bed through the use of occlusive dressings. A moist wound environment facilitates wound healing due to the following reasons:

• Enhanced Autolytic Debridement: A moist wound environment has been found to enhance the migration of neutrophils to the wound site. This facilitates the phagocytosis of bacteria and necrotic debris which aids in autolytic debridement. Autolytic debridement is the removal and breakdown of necrotic tissue through the use of the body's enzyme system. [2] Monocytes are also attracted to the wound site and differentiate into macrophages. Macrophages contribute to the removal of debris and bacteria. As the presence of devitalized tissue can delay healing, its removal accelerates the healing process. 
  

           A study that demonstrated the effects of moist wound healing found increased levels of neutrophils in wounds that recovered             using moist occlusive dressings. There were also increased levels of lysozymes which enhanced the bactericidal effect of             polymorphonuclear neutrophils. [3]

• Reduced Pain: Compared to traditional dressings, dressings that optimize wound moisture have been associated with reduced pain at rest. In addition, a moist wound environment is associated with less painful dressing changes which improve the patient's quality of life. [4]

• Increased Number of Fibroblasts: Compared to dry wounds, a moist wound environment is associated with an increased number of fibroblasts. Fibroblasts are critical in the formation of granulation tissue through the deposition of collagen and elastin. A study comparing the effect of the moist wound dressing in an acute wound with a dry wound dressing demonstrated 60% more fibroblasts in the moist wound. [5] In addition, a moist wound environment is associated with a timely progression of wound healing. A dry wound environment contributes to wound chronicity. 

• Transport of Growth Factors: The wound exudate acts as a transport medium for growth factors and various cytokines. It is hypothesized that a moist wound environment allows for the accumulation of growth factors. These growth factors stimulate the formation of granulation tissue which in turn aids wound healing. [6] Therefore, occlusive dressings should be recommended by podiatrists and wound care specialists for an optimal wound environment.

• Reduced Infection: Despite the concern of increased infection rates in a moist wound environment, the infection rates are considerably less. A study that compared the infection rates in occlusive and nonocclusive dressings demonstrated significantly fewer infection rates in the occlusive dressings (3.2% vs 7.6%). [7] This can be explained by the enhanced bactericidal activity by neutrophils and macrophages in a moist wound environment.

• Faster Rate of Angiogenesis: Angiogenesis refers to the formation of new blood vessels at the wound sites. Angiogenesis is critical in the wound healing process as it allows for the transport of oxygen and nutrients to the new tissue. An increased rate of angiogenesis is observed in moist wound environments at day 3 which decreases in the later stages, signaling a transition to the maturation phase of wound healing. [8]

• Faster Healing: Compared to dry wounds, the healing rate is significantly faster in moist and wet wounds. [9] This is because of the optimal effect of wound moisture in facilitating autolytic debridement, reduced Infection rates, fibroblasts proliferation, and angiogenesis. All of these effects collectively stimulate wound healing.

• Increased Proliferation of Keratinocytes: Keratinocytes have been found to proliferate more rapidly in a moist wound environment. [10] These cells play a critical role in the repair of the epidermis, and the restoration of skin integrity after an injury. Easier migration of epidermal cells results in faster rates of re-epithelialization. 

• Increased Collagen Synthesis: Occlusive, moist wound dressings are associated with increased collagen synthesis. [11] This results in faster and improved wound healing. 

Optimizing Moisture In Wound Environment 

Given the importance of moisture in wound care, it is critical to achieving an optimal balance of moisture in the wound environment. This can be achieved through the use of various occlusive dressings that are currently available. An excess of wound moisture can be detrimental to the wound healing process however due to maceration and skin damage. Therefore, regular assessment of wounds by wound care specialists is essential to ensure that the wound moisture is within the required limits. 

References: 

1. Winter GD, Scales JT. Effect of air drying and dressings on the surface of a wound. Nature. 1963 Jan;197(4862):91-2.
2. Schultz GS, Sibbald RG, Falanga V, Ayello EA, Dowsett C, Harding K, Romanelli M, Stacey MC, Teot L, Vanscheidt W. Wound bed preparation: a systematic approach to wound management. Wound repair and regeneration. 2003 Mar;11:S1-28.
3. Schilling RS, Goodman N. Clinical trial of occlusive plastic dressings. Lancet. 1950;258:293-6.
4. Field CK, Kerstein MD. Overview of wound healing in a moist environment. The American journal of surgery. 1994 Jan 1;167(1):S2-6.
5. Dyson M, Young S, Pendle CL, Webster DF, Lang SM. Comparison of the effects of moist and dry conditions on dermal repair. Journal of investigative dermatology. 1988 Nov 1;91(5):434-9.
6. Chen WJ, Rogers AA, Lydon MJ. Characterization of biologic properties of wound fluid collected during early stages of wound healing. Journal of investigative dermatology. 1992 Nov 1;99(5):559-64.
7. Hutchinson JJ, McGuckin M. Occlusive dressings: a microbiologic and clinical review. American journal of infection control. 1990 Aug 1;18(4):257-68.
8. Doughty DB, Sparks-Defriese B. Wound-healing physiology. Acute and Chronic Wounds: Current Management Concepts. St Louis, MO: Mosby/Elsevier. 2007:307-36.
9. Alper JC, Welch EA, Ginsberg M, Bogaars H, Maguire P. Moist wound healing under a vapor permeable membrane. Journal of the American Academy of Dermatology. 1983 Mar 1;8(3):347-53.
10. Vogt PM, Andree C, Breuing K, Liu PY, Slama J, Helo G, Eriksson E. Dry, moist, and wet skin wound repair. Annals of plastic surgery. 1995 May 1;34(5):493-9.
11. Alvarez OM, Mertz PM, Eaglstein WH. The effect of occlusive dressings on collagen synthesis and re-epithelialization in superficial wounds. Journal of Surgical Research. 1983 Aug 1;35(2):142-8.

‍