Diagnosis

There's no perfect test used to confirm or rule out a food allergy. Your doctor will consider a number of factors before making a diagnosis. These factors include.

• Your symptoms. Give your doctor a detailed history of your symptoms — which foods, and how much, seem to cause problems.
• Your family history of allergies. Also share information about members of your family who have allergies of any kind.
• A physical examination. A careful exam can often identify or exclude other medical problems.

• A skin test. A skin prick test can determine your reaction to a particular food. In this test, a small amount of the suspected food is placed on the skin of your forearm or back. A doctor or another health professional then pricks your skin with a needle to allow a tiny amount of the substance beneath your skin surface.

  If you're allergic to a particular substance being tested, you develop a raised bump or reaction. Keep in mind, a positive reaction to this test alone isn't enough to confirm a food allergy.

• A blood test. A blood test can measure your immune system's response to particular foods by measuring the allergy-related antibody known as immunoglobulin E (IgE).

  For this test, a blood sample taken in your doctor's office is sent to a medical laboratory, where different foods can be tested.

• Elimination diet.You may be asked to eliminate suspect foods for a week or two and then add the food items back into your diet one at a time. This process can help link symptoms to specific foods. However, elimination diets aren't foolproof.

  An elimination diet can't tell you whether your reaction to a food is a true allergy instead of a food sensitivity. Also, if you've had a severe reaction to a food in the past, an elimination diet may not be safe.

• Oral food challenge. During this test, done in the doctor's office, you'll be given small but increasing amounts of the food suspected of causing your symptoms. If you don't have a reaction during this test, you may be able to include this food in your diet again.