How can a food allergy be diagnosed?

It is a good idea that you go see your doctor if you think you or your child has a food allergy. Your doctor will ask you detailed questions about your own or your child's symptoms, such as what they are, when they happen, how severe they are, or how long they last. You may also be asked about how the food that seems to cause the symptoms is cooked or prepared. Your doctor will try to determine what food or foods are causing the symptoms.

There are some tests that can help with the diagnosis. The most reliable diagnostic test for any food allergy is an elimination diet challenge. You must make sure you or your child child does not eat any food which may contain the suspected allergen, and observe to see if the symptoms stop. Your doctor might then ask you to reintroduce foods containing the suspected allergen into your own or your child's diet to see if any symptoms start again. Any elimination diet challenges should be done under close supervision and with the consultation of a dietician or your doctor, and can last a few weeks. There are blood tests and skin tests too.

A RAST (radioallergosorbent test) is done by taking a blood sample and trying to react various allergens with the chemicals (in particular, IgE) in your blood. It is done in the lab, and is quite reliable too. A skin prick test is less reliable and accurate than a RAST, and involves introducing small amounts of allergen to the skin to see if a reaction develops. If you are allergic to the allergens which have been introduced, you might see a “wheal and flare” - an irregular, blanched area of skin surrounded by a reddened area of inflammation.

Food Allergies Guide Index:

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• What are food allergies?
• Who gets food allergies?
• What are some common signs and symptoms of a food allergy?

• What are some common foods that can cause an allergic reaction?
• How can a food allergy be diagnosed?
• How can food allergies be managed?

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