The serum IgE, that are associated to the process of the immediate allergy are studied in children presenting a clinical semiology suggestive of intolerance to the cow-milk proteins, in order to specify their contribution in the diagnosis and the follow-up of this disease. The serum IgE are determined by the PRIST method and the presence of the milk proteins specific IgE, by the RAST method. In infants (n = 80) fed with infant formula and less than 4 months old, if it obviously appeared an increase of the global IgE with the age, on the other hand, no one had specific IgE to the cow-milk proteins. The same methods were used in children presenting a clinical semiology of IPLV. It appeared these children could be separated in 2 groups according to the presence or the absence of extra-digestive symptoms (urticaria...). There is significant increase of the global IgE level and the first group, but not in the second one. The two main allergens more frequently implicated are the alpha-lactalbumin and the beta lactaglobulin. Meanwhile the RAST efficiency is better for the global allergen to the cow-milk. Meanwhile, the determination of the specific IgE to the milk PLV does not present a prognosis interest. In fact, the success of a milk proteins reintroduction is not necessarily correlated with a previous negativation of RAST.