It is not uncommon for me to get this question from parents in my practice,

” Can you order a test to find out what my child is allergic to?”

The answer is yes and no. Before we initiate any test for food allergies, we need to ask ourselves if we have a suspicion that the child is allergic to a certain food or foods.

So, what does an allergic reaction look like?

If you are allergic to something and are exposed to it, your immune system goes crazy and starts to produce chemicals (mostly histamine) that cause the symptoms of allergies. Here are some symptoms:

1. Burning, itchy or tingling sensation in mouth
2. Swelling of lips, tongue, eyes
3. Hives, itchy skin or atopic dermatitis/eczema
4. Severe vomiting, diarrhea, blood/mucus in stool
5. Tightness of throat, chest, difficulty breathing
6. Anaphylaxis: This is a life threatening allergic reaction when 2 or more symptoms are present and may lead to low blood pressure

What is likely not an allergic reaction

1. vomiting after eating something you’ve had before
2. diarrhea after consuming too much sugar
3. rash around the mouth after eating something acidic

Which foods can cause an allergic reaction?

Any food. However, the most common culprits are

1. Cow milk, eggs and peanuts are usual suspects
2. Tree nuts like walnuts, cashews, pecans
3. Fish
4. Seafood, especially shellfish like shrimp, crabs and lobsters
5. Soy
6. Wheat

Of these, peanuts, tree nuts and seafood after most likely to cause a serious allergic reaction.

How are food allergies diagnosed?

First we get the lay of the land- What did the child  eat? How much did they eat? What were the symptoms? How soon did they start and how long did they last? Is there a family history of food allergies?

Based on your answer to these questions, I may either come to the conclusion that this was not an allergic reaction or that it may have been. In the latter scenario, I will refer you to a  Pediatric Allergist.

What should you expect at the allergist visit?

Make sure you stop any allergy medications 1 week prior to the visit. Expect to answer a lot of the same questions that I already asked (Pediatricians like to talk). Based on their assessment they may do one or more of the following tests

1. Blood test to look for antibodies to specific allergens
2. Skin test to look for reaction to specific allergens: This test is more exact that the blood test
3. Food challenge: Looking for reaction after eating suspected allergen
4. Food elimination: Eliminating all the usual food allergens and then introducing them one at a time to see which one causes the symptoms

And that is how we diagnose a food allergy.