Cow’s milk and hen’s egg are among the most common triggers of IgE-mediated allergic reactions in childhood. Since not all IgE sensitizations are clinically relevant, it is important to confirm or exclude manifest allergy. Thereby the burden of an elimination diet will be restricted to only those cases where such a measure is essential. A number of proteins have been identified in cow’s milk and hen’s egg as single allergens (Bos d 1–12 in cow’s milk and Gal d 1–6 in hen’s egg). However, measuring IgE to these single allergens does neither predict on clinical relevance nor prognosis of the individual allergy. In terms of ascertaining whether cooked hen’s egg is tolerated, measuring sIgE to ovomucoid (Gal d 1) can be useful. Measuring sIgE to lysozyme (Gal d 4) can be helpful to decide whether lysozyme-treated foodstuffs (e. g., cheese) should be avoided. Single allergen determination is not able to answer the question of whether cow’s milk or hen’s egg are tolerated in baked form (e. g., in muffins). If the foodstuffs in question are tolerated in baked form, their regular consumption has a favorable effect on prognosis.