The aim of the investigators study is to show the efficacy, tolerance and nutritional adequacy of a newly developed thickened extensively hydrolyzed formula in infants with a proven cow's milk protein allergy. In all included patients, cow's milk protein allergy will have been diagnosed based on a double blind placebo controlled food challenge, considered as golden standard in cow's milk protein allergy diagnosis. To evaluate efficacy of the formula, the formula has to be tolerated by at least 90% (with 95% confidence) of cow's milk protein allergy infants following literature consensus. A symptom diary will be filled out for this purpose by the patients' parents or legal guardians and the patient will be followed clinically by his doctor several times during the study period.