How To Find Out What Foods Your Child Is Allergic To

A food allergy is a serious medical condition where your body’s immune system reacts to certain foods like they’re invaders. If your child has food allergies, an essential part of keeping them safe is knowing which foods trigger a reaction so you can avoid them. A healthcare provider can help you learn which foods your child is allergic to through food allergy testing. 

Food allergy testing involves different tests to help healthcare providers find the specific foods that trigger your child’s allergic reaction. If you see a primary care provider, they will likely refer you to an allergist (a doctor specializing in diagnosing and treating allergies) to do the testing.

Food allergy testing may be recommended for certain cases, including the following:

• Allergic reaction symptoms: A healthcare provider may recommend food allergy testing if your child has symptoms within minutes to an hour of eating a specific food. Food allergy symptoms include nausea, stomach pain, coughing, runny nose, or rash. 
• Anaphylaxis: Allergy testing is often even more important if your child has any signs of anaphylaxis (a life-threatening reaction that can cause swelling of the mouth and throat as well as dizziness, clammy skin, and difficulty breathing). 
• Risk factors: Food allergy testing is also sometimes helpful for children with medical conditions related to food allergies, such as eczema or allergic asthma. 
• Symptoms decrease: Repeat allergy testing is also sometimes helpful to see if your child has outgrown an allergy.

Food allergy testing generally isn’t recommended for children who haven’t shown signs of food allergies. That’s because allergy skin and blood tests can cause false positives. That means the test can sometimes say that your child is allergic to a food even if they’re not. 

Several tests can help check for food allergies. The choice usually depends on your child’s specific symptoms, what tests may be available, any previous test results, and your personal preferences.

Before any test for food allergies, it’s important to ask the healthcare provider if your child needs to stop using any medications. For example, a child taking an antihistamine like Zyrtec (cetirizine) may need to stop taking it for a few days before their test.

Food Elimination Diet

Food elimination diets are an informal type of food allergy testing that you do at home with your healthcare provider’s guidance. You remove all suspected foods from your child’s diet for a couple of weeks or longer. Then, you slowly start adding foods back, one by one, and see what symptoms may occur.

How to prepare: Talk to an allergist or other healthcare provider about whether an elimination diet is safe for your child. They can also discuss what foods to eliminate and what schedule to use to reintroduce foods. 

What to expect: During the testing period, you keep track of the foods your child is eating and note any symptoms that appear. If symptoms decrease while a food is avoided and come back after reintroducing the food, an allergy is likely.

Risks and considerations: This approach may not be appropriate for all children, including those who’ve had more serious anaphylaxis-type reactions. These children usually need a more definitive diagnosis and monitoring.

Skin Prick Test

A healthcare provider does a skin prick test at their clinic. This test checks for a skin allergic reaction to an injected food allergen to determine whether your child is showing an allergic response. This test can often check for multiple allergens at once.

How to prepare: Ask your healthcare provider if your child should stop taking any allergy medications before the test.

What to expect: The healthcare provider places a small amount of a suspected allergen on your child’s skin, usually on their arm or back. Then, with a needle, they prick the skin so the allergen gets under the skin’s surface. It may be a little uncomfortable, but it shouldn’t hurt much. If the skin develops a raised bump within about 20 minutes, your child may have that allergy.

Risks and considerations: Skin prick tests have a small risk of causing anaphylaxis. Avoid the test if your child has had an anaphylactic response in the last four to six weeks. Skin prick testing shouldn’t be done on children under 2 years.

Specific IgE Blood Test

Blood tests can check for antibodies against specific food allergens. The specific IgE blood test checks for a kind of antibody called IgE, which is a key component of allergic reactions. The test can help identify specific food allergies, such as sesame or peanut allergies.

Specific IgE blood tests may be a good option if your child has a history of anaphylaxis or if they have a skin condition that might make it difficult to interpret a skin prick test. A blood test can also be helpful if an initial skin prick test didn’t find anything but you or your healthcare provider still suspect an allergy.

How to prepare: There is no specific preparation needed for this test.

What to expect: After cleaning the area where they’ll insert the needle, a technician takes a small amount of blood from a vein in your child’s arm. This may sting a little. The blood sample is usually analyzed at a separate center, so results can take a few days to come back. Blood from a single blood draw can be used to test multiple potential food triggers.

Risks and considerations: Like any blood draw, this test has a small risk of infection or bruising. It carries no risk of anaphylactic response. 

Oral Food Challenge

An oral food challenge is considered the gold standard for allergy diagnosis because it’s more accurate than other tests. However, it is more costly and time-consuming than other tests, so healthcare providers or parents may sometimes choose not to do it.

How to prepare: Talk to your healthcare provider about stopping any allergy medications before the test.

What to expect: Under careful observation and with access to medical treatment, the healthcare provider will give your child a small amount of the suspected allergen food. Over the next several hours, your child may eat increasing amounts of the suspected allergen until mild symptoms occur. If your child has symptoms, the challenge usually stops.

Risks and considerations: The oral food challenge poses a risk of anaphylaxis. If serious symptoms occur, your child might need to receive emergency treatment with epinephrine. Because you’ll be in a medical facility, healthcare providers can give your child this treatment right away.

Along with a review of your child’s symptoms and a physical exam, allergy tests can be useful in figuring out whether your child is allergic to a specific food. Not every child needs formal testing, but skin prick tests and blood tests can help determine if an allergy is likely. If needed, an oral food challenge can be used to make a definitive diagnosis.