Thirty seven breast fed infants with eczema were studied to see whether changes in their mothers' diets affected their skin condition. Nineteen mothers and babies took part in a double blind crossover trial of exclusion of egg and cows' milk, and 18 took part in open exclusion of 11 foods followed by double blind challenge to those mothers whose infants seemed to respond. Babies were examined at the beginning and end of each dietary period, and the extent and severity of the rash were given a numerical score. The eczema improved in six infants when their mothers avoided egg and cows' milk and worsened again when these were reintroduced. Two infants suffered gastrointestinal reactions after maternal ingestion of egg and cows' milk, one developing colitis. Maternal dietary exclusion seems to benefit some breast fed babies with eczema.