How best to diagnose milk allergy? skin test or blood test?

Milk allergy: Milk protein allergy is a recognized problem in the first year of life; cow’s milk protein allergy is the most common such allergy. Diagnosis is suspected on history alone, with laboratory evaluations playing a supporting role. Confirmation requires elimination and reintroduction of the suspected allergen. Management includes diet modification for nursing mothers and hydrolyzed formulas.

Probably skin.: If someone is allergic to some allergen, like milk, a skin test can be done to see if there is reaction to it. Swelling and redness of the site can tell how severe it is. Clinical labs may be able to test reactions serologically, so blood might be taken also for this.