Some factors affecting skin and wound healing

The domestic pig is the preferred animal for studying the effects of environmental factors on skin and wound because its integument is more like that of man than any other. The three factors that most drastically affect the pattern, speed and quality of healing are dehydration of exposed tissues, the status of the blood supply bringing oxygen and nutrients to the area and sepsis. Wounds exposed to the air lose water vapour, the upper dermis dries and healing takes place beneath a dry scab. Covering a wound with an occlusive dressing prevents scab formation and radically alters the pattern of epidermal wound healing. Blowing on wounds creates a scab within three hours instead of the normal 24 hours but more tissue is sacrificed in the process. This may only be justified if it can be shown that rapid artificial scab formation significantly cuts down the incidence of severe infections, i.e. in large burns. Less serious wounds heal faster when covered with a suitable occlusive dressing. Indolent wounds are characterised by a rim of infected, necrotic tissue in which leucocytes and macrophages are unable to function effectively through lack of oxygen. A suitable dressing changed frequently can bring about mild debridement and re-establish the conditions for healing.