Diaper rash

Irritant diaper dermatitis or more colloquially diaper rash is a group of disorders related to an inflammatory response to any of several irritants that result from the wearing of diapers.  It is exacerbated by the damp environment and can be caused by a reaction to urine, or a bacterial or fungal infection, but is usually a reaction to exposure to the infant's own stool.
Diaper rash is characterized by a pair of symmetrical rashes that run the length of the fattest part of the buttock where the buttocks are in continuous and direct contact with the diaper. However, if it is complicated by bacteria or fungus, it can spread beyond these surfaces.  Pustules are also common.  It usually does not affect the anus.
A differential diagnosis should exclude seborrhoeic dermatitis, which is characterized by oily yellowish scales, and eczema, which is accompanied by an itch.  These require different treatment.
Although stool is usually the source of the rash, urine can make it worse as the ammonia from the breakdown of urine can speed up the action of the enzymes in the stool.  
Diaper rash is less common in breast fed babies.  It is believed that this is due to levels of the enzymes that result in the rash and the lower pH of the urine.  
An infant with diaper rash should ideally stop wearing diapers until the skin is thoroughly dry, and thereafter diapers should be changed quickly to prevent recurrence.  Drying powders, such as talcum and starch, should be avoided as they can cause complications and can even encourage fungal growth.  Ointments such as petroleum jelly and zinc oxide are often helpful in both prevention and treatment.
Irritant diaper dermatitis at Wikipedia
Diaper rash
Category:Dermatology
Category:Pediatrics