We studied 44 children, 7 months to 14 years old (15 males and 29 females), diagnosed for food allergy from the symptomatology, anamnestic data information, physical examination, determination of IgG/IgA/IgE plasmatic levels, and the application of the Prick test and RAST. The anamnestic data revealed a high prevalence of cow's milk feeding during the first 6 months of life, and a high incidence of allergies in the family, the mother being the most frequently affected relative. The children had a low IgA plasmatic level (56.78 +/- 6.3 mg%) and a high IgE plasmatic level (389 +/- 35 U/ml). RAST proved to be positive only in 28% of the subjects; the Prick test showed a better correlation with the symptomatology. The children were divided into groups A and B and submitted to an exclusion diet for 6 months, group B receiving oral Thymomodulin. At the end of this treatment period, a better food tolerance was achieved in the group of children treated with Thymomodulin combined with the exclusion diet. The oral challenge which induced a relapse of clinical symptomatology in 68% of the subjects in group A, induced it in only 29% of the subjects in group B. Furthermore, clinical manifestations were less severe in group B. In the group B children, the IgE plasmatic level showed a significant decrease (228 +/- 6 U/ml) (p less than 0.005), and the IgA plasmatic level rose to 98.35 +/- 8 mg% (p less than 0.01). No modifications were observed in the other immunological parameters studied. It is concluded that oral Thymomodulin combined with an exclusion diet was very effective in preventing food allergy relapses.