The outermost layer of the skin, the stratum corneum (SC), is slightly acidic. This “acid mantle” is maintained by endogenous phospholipids secreted by lamella bodies at the edge of the SC and by exogenous free fatty acids from bacterial lipase and sebaceous glands, and eccrine gland secretions. The finely tuned interplay of these factors produces a normal skin pH between 4.5 and 5.5. As skin pH approaches neutral values, acid mantle function is disrupted:
- Pathogen growth increases, inflammatory cytokines are released, and antimicrobial barrier is impaired
- Epidermal barrier function is altered and SC integrity and cohesiveness is compromised
Abnormalities in perianal and vulvovaginal skin pH often are the result of irritation and injury caused by chemicals in personal hygiene products or by diarrhea, constipation, hemorrhoids, and anal fissures associated with gastrointestinal or vaginal conditions such as infection, chronic disease, functional abnormalities, or hormonal changes during pregnancy or menopause. Skin irritation and injury of perianal and vulvovaginal skin can make appropriate cleansing painful, and impaired antimicrobial defense of the skin can lead to continued inflammation and delayed healing.