
Except for a few specific localized areas, human skin normally ranges from pH 4.2–6.0 due to the abundance of fatty acids that are present. Skin should be slightly acidic - women with an alkaline stratum corneum (the skin's outermost layer) develop more fine lines and crow's-feet—and are more prone to sun damage—than those with acidic skin. On the other hand, excess fat could attract microbes causing acne.