pH and Microbial Infections.

Maintenance of an acidic stratum corneum pH is a major component of the skin's protective system and creates a hostile environment for colonization with pathogenic microorganisms. This barrier can however be overcome on healthy and in particular on compromised skin. Mycosis, diaper/incontinence dermatitis and wound healing are examples of cases where microbial infection is promoted by the altered skin conditions or environment. Fungi have a complex system that senses ambient pH that leads to metabolic responses allowing adhesion, growth and invasion, as microbial metabolites further increase skin pH resulting in a clinically manifest infection (mycosis). Diabetic patients with a higher pH in intertriginous areas are particularly vulnerable to candidiasis. In diaper and incontinence dermatitis, the increase in skin pH and damage to the skin barrier function is triggered by the contact with urine and faeces with or without occlusion and maintained by host and microbial enzymes and metabolites. This leads to the reduction of the protective resident microflora and fungal overgrowth, mostly with Candida albicans. Skin care with slightly acidic products may help to prevent and treat this kind of dermatitis. Wound healing is a complex sequence of biologic events correlated with ambient pH, which influences the different phases of the healing process. The pH determines the appropriate activity of immune cells and key enzymes as well as biofilm formation. Chronic wounds emerging from the disruption of the healing process are characterized by a neutral to slightly alkaline pH and may benefit from wound pH monitoring and therapeutic acidification.