Medical information for patients

Nappy rash

Nappy rash, otherwise known as napkin or diaper rash, is a red rash, or sore area, that affects skin under or around a baby's nappy.


There may be a little redness, but the area may become very sore and red, with red spots, blisters and broken skin.


The cause of nappy rash is the skin being kept wet along with the chemical irritation of ammonia produced by stale urine. This has the effect of breaking down the protective barrier normally formed by the skin, causing redness and rawness (inflammation) and allowing germs of various types to attack.

The most common infection to complicate the ammonia-like irritation is thrush (candida). In this event, the rash often has clusters or red spots around the margins of the main red area. Other germs (bacteria) can also infect the area.

It follows that the longer wet or soiled nappies are left in contact with the baby's skin, the more likely nappy rash is to develop. Some babies' skin is, however, much more sensitive than others. The problem is probably worse with old fashioned terry towelling nappies, especially if worn with waterproof underpants. Modern disposable nappies, which are better at keeping the fluid away from the skin, are better in some respects.

Other Factors

If using terry nappies, the detergent or softener might remain in the towelling, even after a full wash cycle. (Try smelling and wringing them while still damp. Often bubbles still appear.) Babies with sensitive skin may react to even minute amounts of these chemicals, especially if they contain a "biological" additive.

Babies may react to the elastic at the waist and legs of disposable nappies, and also to other components, but this is only rarely a problem.


Persistent nappy rash problems can come as a result of sensitivity to agents used in washing towelling nappies, and it is worth avoiding anything containing biological ingredients and trying a double rinse cycle.


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