Four cases of infants with atopic dermatitis are reported. In all cases, a sensitization to peanut is demonstrated. Any ingestion of peanuts can be excluded, with the exception of a daily consumption of peanut oil, contained in milk formulas. Oral challenges with peanut oil induce a rash, and elimination of these brands is followed by the disappearance of eczematous lesions. The presence of residual allergenic proteins in peanut oil is thus suspected. Owing to the growing incidence of peanut hypersensitivity, the elimination of peanut oil from all milk formulas, food for babies, and ointments, seems to be highly advisable.