To date the most reliable procedure for the diagnosis of milk hypersensitivity is a properly conducted elimination-challenge test. Several in vitro tests have been developed but because of the diverse underlying mechanisms of hypersensitivity reactions to milk developing a single laboratory test that can be universally positive in every patient would be rather difficult. However, with a better categorization of milk-sensitive patients, together with the development of relevant, standardized and practical tests, the laboratory diagnosis of milk allergy should become more reliable. Milk hypersensitivity can be effectively treated and is largely preventable. Avoidance is the most effective mode of treatment and results in a good prognosis. In instances where the desired degree of avoidance cannot be attained pharmacologic agents may be of help. The need still exists for developing an effective procedure of hyposensitization. For prevention, prolonged breast feeding should be recommended, especially in infants of atopic families.