Background: The prevalence of food allergy increased worldwide in the last century. In Chile we became aware of this increase 10-15 years ago, after an epidemiological transition on health. Aim: To assess the most frequent clinical presentations of food allergy, results of circulating immunologlobulins (total IgE, specific IgE and IgG4 against cow's milk) and usefulness of a standardized challenge test. Patients and methods: Cross sectional assessment of 49 patients with cow's milk allergy (9 months - 8 years of age), diagnosed at INTA, University of Chile between 1991-2001. Results: All patients had cow's milk allergy and 37% of them were additionally intolerant to other allergens. Seventy eight percent had digestive symptoms and 84% had non digestive symptoms. The cause of consultation was a non-digestive manifestation in 16% of cases. At least one of the immunoglobulins (total IgE total, specific IgE or IgG4) was over the cut off point in 92% of patients. Between 1990-1995 six patients were diagnosed with cow's milk allergy and malabsorption syndrome. Suppression of the specific allergen resulted in disappearance of symptoms in 78% of patients; when a second dietary modification was necessary 87% of cases showed a good response. Thirty five of 56 challenge tests performed were done at home, by relatives, in a non-controlled fashion. All of them were aimed to determine the desensitization of the child. Conclusions: Digestive and non-digestive manifestations were observed in these patients with food allergy. Although not designed to assess laboratory tests, results show that serum immunoglobulin determinations were helpful in guiding diagnosis. Mothers and relatives should be educated to accept diagnostic challenges and avoid carrying out non-controlled challenges (Rev Méd Chile 2003; 131: 275-82).