Nappy rash is an irritant contact dermatitis affecting the skin where the moist nappy is in contact. It spares intertriginous areas. An allergic rather than irritant contact dermatitis can occur, but is uncommon in children <2 years. Change nappies 6-8 times a day, dry thoroughly, use barrier eg zinc oxide cream. Differential diagnoses to be considered also include candidiasis, atopic dermatitis, psoriasis, intertrigo, bullous impetigo and the rare Langerhans cell histiocytosis.
Infantile seborrhoeic dermatitis can affect the nappy area but tends to affect the creases. It tends to be salmon coloured with greasy yellowish scale. There may be seborrhoeic dermatitis elsewhere, for example the face and scalp (cradle cap).