Nappy rash (irritant dermatitis) is a term used to describe skin rashes in the nappy area that are caused by various skin irritants.
Irritant dermatitis is characterised by joined patches of erythema (redness) and scaling mainly seen on the convex surfaces, with the skin folds spared.
Nappy rash with secondary bacterial or fungal involvement tends to involve the skin folds.
Nappy rash develops when skin is exposed to prolonged wetness, increased skin pH caused by urine and faeces, and resulting breakdown of the stratum corneum (outermost layer of the skin). In adults, the stratum corneum is composed of 25 to 30 layers of flattened dead keratinocytes, which are continuously shed and replaced from below. These dead cells are interlay with lipids secreted by the stratum granulosum just underneath, which help to make this layer of the skin a waterproof barrier. The stratum corneum's function is to reduce water loss, repel water, protect deeper layers of the skin from injury and to repel microbial invasion of the skin. In infants, this layer of the skin is much thinner and more easily disrupted.
Although wetness alone macerates the skin, softening the stratum corneum and greatly increasing susceptibility to friction injury, urine has an additional impact on skin integrity because of its effect on skin pH. While studies show that ammonia alone is only a mild skin irritant, when urea breaks down in the presence of faecal urease it increases skin pH, which in turn promotes the activity of faecal enzymes such as protease and lipase. These faecal enzymes increase the skin's permeability to bile salts and act as irritants in and of themselves.
The interaction between faecal enzyme activity and irritant dermatitis explains the observation that infant diet and nappy rash are linked, since faecal enzymes are in turn affected by diet. Breast-fed babies, for example, have a lower incidence of nappy rash, possibly because their stools have lower pH and lower enzymatic activity (Hockenberry, 2003). nappy rash is also most likely to be diagnosed in infants 8–12 months old, perhaps in response to an increase in eating solid foods and dietary changes around that age that affect faecal composition. Any time an infant’s diet undergoes a significant change (i.e. from breast milk to formula or from milk to solids) there appears to be an increased likelihood of nappy rash (Atherton and Mills, 2004).
Infants are more susceptible to developing nappy rash after treatment with antibiotics, which affect the intestinal microflora. Also, there is an increased incidence of nappy rash in infants who have suffered from diarrhoea in the previous 48 hours, which may be due to the fact that faecal enzymes such as lipase and protease are more active in faeces which have passed rapidly through the gastrointestinal tract.
The most effective treatment, although not always the most practical one, is to discontinue use of nappies, allowing the affected skin to air out.
Other commonly recommended remedies include oil-based protectants, often using various over-the-counter "nappy creams", but sometimes people use petroleum jelly and shark liver oil or cod liver oil; zinc oxide based ointments, and, in extreme cases, anti-fungal cremes.
Low concentration hydrocortisone creams are also sometimes used to treat the symptoms of nappy rash, although they do little to clear up the rash itself.
Other rashes that can occur in the nappy area include seborrhoeic dermatitis and atopic dermatitis:
* Seborrhoeic dermatitis, typified by oily, thick yellowish scales, is most commonly seen on the scalp (cradle cap) but can also appear in the inguinal folds.
* Atopic dermatitis, or eczema, is associated with allergic reaction, often hereditary. This class of rash may appear anywhere on the body and is characterised by intense itchiness.
[br]: wikipedia GFDL
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