The main reason for the development of milk Allergy is a more pronounced than normal reaction of the immune system to this substance. Normally, the body never collides with whole milk, except for breast-feeding women. However, the milk formed in their mammary glands does not cause increased immune reactivity due to the fact that immune cells recognize it as an integral part of the body and do not attack. However, getting into the gastrointestinal tract of a child or an adult, milk, before it is sucked into the intestine, disintegrates into many components. The components are simple amino acids, fatty acids and carbohydrates, which the body has met before and does not consider dangerous to itself. The Allergy of the body milk develops only in the case if some or all of its component parts unchanged to penetrate into the bloodstream and face at least one cell of the immune system.