Summary: Cow's milk protein allergy is the most common type of food allergy in children, with a growing trend of occurrence. It can proceed in both the IgE-mediated and the non-IgE-mediated mechanism, hence the clinical symptoms are truly diverse. They include gastrointestinal, skin, and respiratory system ailments as well as general symptoms in the form of anaphylactic reaction. The diagnosis, especially of the non-IgE-mediated form, can be difficult. It is essential to demonstrate a cause-and-effect relationship, namely improvement on a dairy-free diet and deterioration after oral exposure to milk allergens, i.e. a positive oral food challenge. The diagnosis of cowʼs milk protein allergy requires a dairy-free diet. Milk is a crucial component of the diet of infants and young children, therefore the elimination of milk from the diet must be associated with its appropriate supplementation. A dairy-free diet should be followed until tolerance is achieved, the duration of which varies. The physician deciding whether to use it or to defer it should remember about the consequences. An unnecessarily introduced dairy-free diet may carry a risk of nutritional defi-ciencies, developmental disorders, reducing the quality of life, developing feeding disorders and provoking acute allergic reactions. In turn, the consequence of improper diagnosis/misdiagnosis of cowʼs milk protein allergy is the patientʼs exposure to the possibility of an anaphylactic reaction and a range of disorders resulting from ongoing allergic inflammation. Based on international and Polish guidelines and the authorsʼ own experience, the paper discusses the principles of diagnosis and treatment of children with cow's milk protein allergy.