Perhaps more than any other kind of allergen, search for a food allergen seems to be difficult. There should be no bias about the usual allergens found in our food, that are a source of pathology that is less spectacular than shocks or giant urticaria that are provoked by easily recognised causes. Crossed allergies must be recognised in their overall features. This may give decisive aid in the etiological approach by facilitating understanding of the symptoms and the discovery of potential triggering allergens which are systematically sought.