Negative Skin Prick Test To Milk: You May Still Have A Milk Allergy

There are 2 types of food allergy.

1) IgE-mediated milk allergy (risk of anaphylaxis, need to carry epinephrine).
2) non-IgE mediated milk allergy (delayed onset, mostly gut related symptoms, not anaphylactic).

Skin prick test can only help with diagnosing an IgE milk allergy. Just because you have a negative skin prick test to milk does not mean that you don't have a milk allergy. Just the other kind that does not typically lead to anaphylaxis. Symptoms are mostly gut related, such as vomiting and diarrhea, and failure to thrive.

There is no testing for non-IgE food allergy. It is based on solely symptoms when the allergen is introduced or removed. The gold standard for diagnosing a non-IgE food allergy is to remove the suspicious food to see if symptoms go away AND then reintroduce the food again. If symptoms return, that confirms the diagnosis. Many times parents skip the last step (for obvious reasons).

I have seen babies with negative skin prick test being misdiagnosed with lactose intolerance. These babies still get symptoms even after switching to lactose free cow's milk or formula. Lactose intolerance happens when the body cannot breakdown the lactose sugar in milk. Milk allergy is a reaction to milk proteins. Hope this explanation helps!