Two sisters, aged 5 and 6 years, were admitted to the hospital because of growth retardation accompanying supposed multiple food hypersensitivity. The older girl had asthma. Her symptoms had given cause for several non-regular practitioners to diagnose her and subsequently her sister as having 'food hypersensitivity'. The diet they were put on was further restricted by their parents when the symptoms did not subside. The diet was shown to be very monotonous and the energy supply was only half of the recommended daily allowances. Stepwise normalization of the diet was achieved and both girls showed catch-up growth in the following years. Food hypersensitivity has a considerably higher incidence when self reported than when diagnosed according to established criteria (elimination, provocation, re-elimination). Dietary changes in children should always take place under the supervision of a dietician, who can ensure that the diet is nutritionally adequate.