A prototypical example of irritant contact dermatitis, diaper dermatitis is caused by overhydration of the skin, maceration, prolonged contact with urine and feces, retained diaper soaps, and topical preparations. Signs and symptoms are restricted in most individuals to the area covered by diapers.
Diaper rash affects the areas within the confines of the diaper.
Increased wetness in the diaper area makes the skin more susceptible to damage by physical, chemical, and enzymatic mechanisms. Wet skin increases the penetration of irritant substances. Superhydration urease enzyme found in the stratum corneum liberates ammonia from cutaneous bacteria. Urease has a mild irritant effect on nonintact skin. Lipases and proteases in feces mix with urine on nonintact skin and cause alkaline surface pH, adding to the irritation.