Background: Nappy rash accounts for 20% of dermatology consultations in childhood, but its causes are poorly understood.
Aim: To determine the incidence of nappy rash during the first four weeks of life in a geographically defined United Kingdom (UK) population, and to study the factors associated with developing the rash.
Method: The data are derived from self-completed questionnaires of parents in the Avon Longitudinal Study of Pregnancy and Childhood (ALSPAC). The response rate to a questionnaire about the child administered four weeks after delivery among parents of singleton infants was 87% (12103/13902).
Results: The incidence of nappy rash was 25%. Fourteen highly significant possible causal factors emerged, of which 10 were retained in a logistic regression model: dirtying of nappy, contact with doctor about other problems, history of rashes in joints or skin creases, type of nappy worn, being fed cereal, taken to mother's bed when waking at night, history of cradle cap, general state of health, previous stomach upset, and being only breast-fed. However, the relative risks were generally small.
Conclusions: The likelihood of nappy rash increases with intercurrent illness and early introduction of cereals. Disposable nappies give little protection, and this finding helps to endorse a recently introduced hospital scheme arising from environmental concerns that encourages parents to use cotton nappies instead of disposables. For many babies, however, the causes of nappy rash remain unknown.