The perinatal period has been described as a window of increased susceptibility for allergic sensitization. Avoidance of allergenic proteins by extended breast feeding and delayed onset of weaning is generally agreed to be beneficial. Case reports indicate however that dietary proteins may be transferred to the mothers milk and cause atopic symptoms. This study looked at the effect of a maternal allergen exclusion diet during lactation alone on the development of atopy in infants with a similar weaning regimen. Families were recruited when one or both parents was atopic. The maternal exclusion diet group (n=15) and the normal diet group (n=96) were self selected. Infants were assessed at 3,6,12 and 18 months and skin prick tests performed at 6,12 and 18 months. Eczema and eczema associated with food sensitivity tended to be more frequent in the maternal diet group, although the differences did not reach statistical significance. Despite the advice that infants should not be given egg before 12 months of age 40% of the infants with eczema had positive skin prick test results to egg at 6 months and 33% at 12 months. In the whole study group the frequency of food associated eczema was higher in first born infants (p=0.04) at 6 months of age. This pilot study indicates that maternal elimination diet during lactation alone is not beneficial. This may be due to the importance of genetic factors, in utero sensitization or post birth sensitization through inhalation or ingestion.