Diagnosis

When food causes an allergic reaction, it isn't always easy to pinpoint what food is to blame. To evaluate whether you or your child has milk allergy, your doctor may:

• Ask detailed questions about signs and symptoms
• Perform a physical exam
• Have you keep a detailed diary of the foods you or your child eats
• Have you eliminate milk from your diet or your child's diet (elimination diet) — and then have you add back the food to see if it causes a reaction

He or she may also recommend one or both of the following tests:

• Skin test. In this test, your skin is pricked and exposed to small amounts of the proteins found in milk. If you're allergic, you'll likely develop a raised bump (hive) at the test location on your skin. Allergy specialists usually are best equipped to perform and interpret allergy skin tests. Keep in mind that this type of test isn't completely accurate for detecting milk allergy.
• Blood test. A blood test can measure your immune system's response to milk by measuring the amount of immunoglobulin E (IgE) antibodies in your blood. But this test isn't completely accurate in identifying a milk allergy.

If your examination and test results can't confirm milk allergy, your doctor might administer an oral challenge, in which you are fed different foods that may or may not contain milk in increasing amounts to see if you react to the ones that contain milk. It's a good idea to have allergy tests administered by an allergist who's been trained to manage serious reactions.

If your doctor suspects that your symptoms are caused by something other than a food allergy, you may need other tests to identify — or rule out — other medical problems.