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How To Find Out If You Have A Food Allergy: Steps And Options To Consider

How To Test For A Food Allergy

If you suspect a food allergy, avoid self-diagnosis and head to a doctor to be tested. A skin prick test or blood test that checks for IgE antibodies, a sign of an allergic reaction to a food, can help pinpoint allergies. An oral food challenge or elimination diet may also be suggested.

An estimated 15 million Americans have food allergies and 5.9 million of them are children or teens under 18.1 Food allergies can range from the mildly uncomfortable to full-blown medical emergencies, so it is important to know what your body may react to. While you may be aware of some allergies, not all of them are obvious enough to notice. So is there a way to test for food allergies at home? What are your alternatives if you suspect an allergy?

Food Allergies Can Cause Hives, Swelling, Vomiting, or Even Anaphylaxis

While there are over 170 known food allergens, eight of them are responsible for most food allergies in the United States. These are milk, eggs, tree nuts, peanuts, soy, wheat, fish, and crustacean shellfish.2

When your body’s immune system triggers an abnormal response to a certain food or drink, it is dubbed a food allergy. Symptoms of an allergic reaction may include:

  • Rashes and itchy raised skin (hives)
  • Itchiness in the mouth, throat, or ears
  • Swelling in the face, especially around the eyes/lips/roof of the mouth/tongue
  • Abdominal pain and vomiting

If the reaction is more severe, it can cause what’s called anaphylaxis. This is marked by breathing trouble, swelling in the tongue, dizziness, wheezing, persistent cough, tightness in the throat/mouth, feeling lightheaded, feeling faint, or loss of consciousness and must be attended to immediately and treated as a major medical emergency. Children may turn floppy or pale.3 4 Without intervention, an anaphylactic reaction can even result in death.

Most Common Food Allergies: There are certain foods you are more likely to be allergic to and these tend to trigger such abnormal responses in people more than other foods do. They include things like:5

  • Fish
  • Shellfish
  • Peanuts
  • Tree nuts like walnuts, hazelnuts, brazil nuts, or almonds

In addition to these foods, children may also have allergies to things like:

  • Eggs
  • Milk
  • Soy
  • Wheat

Testing For A Food Allergy At Home Is Dangerous

You might think the simplest way to know if you are allergic to a food is to see if you react to it after consuming it. Unfortunately, this can be quite risky if you do have a major allergy and might even prove fatal. Equally problematic in the long run is the misdiagnosis of an allergy through self-testing. For instance, you may think you or your child is allergic to a certain food when, in fact, the cause of the reaction could be an underlying medical condition like Celiac disease or Crohn’s disease. If a health issue is to be blamed for your discomfort, it needs to be diagnosed and treated by a doctor.

Even if you don’t have a health problem, but have cut off certain foods and restricted your diet to avoid the suspected food allergen, it could be bad for your health. A restricted diet could put you at risk of other problems like malnutrition or deficiency diseases.6

Note Symptoms And Onset And Discuss These With Your Doctor

On the other hand, if you have eaten a certain food and suspect that is responsible for the rash you have developed or the stomach upset you’re experiencing, you can discuss this with your doctor during a consultation. This will help them work out if that could be the cause. Your doctor will typically take your medical history and ask questions about how you reacted to the food.

You can take special note of these things:7

  • All symptoms experienced after eating a particular food
  • When the symptoms began – how soon after eating the food?
  • How often this has happened – every time you eat the food?
  • What quantity of food triggers this reaction?
  • How you’ve managed the symptoms – Did you take any medicine to treat it?

A Skin Test For Food Allergies May Be Suggested By Your Doctor

If you’re going to be tested for your food allergies via a skin test, remember to stop taking antihistamines before the blood test since they can interfere with the results. If stopping the antihistamines isn’t possible due to adverse symptoms, you may need to opt for a blood test instead.8

Skin prick tests check for the presence of the immunoglobulin E (IgE) antibody which interacts with the food allergen and causes allergic symptoms. To test for this, you will need to head to your doctor’s office. If you’re squeamish about blood or pain, you needn’t worry – this test is like a minor scratch on the skin, is virtually painless, and doesn’t cause any bleeding. And that’s why it is ideal if you have a fear of needles or if you want instant answers. Here’s what you can expect:9

  • First, a drop of a solution will be placed on either your forearm or your back. This will have either the food allergen being tested or the food itself.
  • A small needle or plastic probe is then used to gently scratch or prick the skin. This is to let a small bit of the food or solution enter the area just beneath the surface of your skin. It will feel a bit like you’ve scratched yourself with a long fingernail.
  • The test results appear in around 30 minutes. If you have a white bump or wheal surrounded by a circle of reddish skin that feels itchy, you are allergic to the food. When no wheal appears, it is considered a negative test result and you are not likely to be allergic to the food.

Just remember, while the negative results can be relied on, about 50–60 percent of positive results may be “false positives.” That’s because foods that trigger a reaction on the skin may not pose a problem after being broken down by your digestive system. Your doctor might prescribe some additional tests to confirm.

Blood Tests Are Another Standard Option For Food Allergies

Blood tests are another option your doctor might suggest to test for allergies. A blood test is a little more expensive and takes a day or two to come back. However, if skin rashes are one of your allergic symptoms or if you are on antihistamines, the blood test will be more suitable.10

One of the customary tests for a food allergy is a blood test for total IgE or specific IgE. The first test checks for the overall IgE antibody levels in your blood while the second checks for specific IgE antibodies that are produced in response to individual allergens. Here’s what you can expect with these tests:11

  • As with any blood test, the healthcare professional taking your sample will draw blood from a vein in the arm via a small needle.
  • The blood collected in a vial or test tube is then sent for testing.
  • The test itself is minimally painful with just a momentary sting when the needle is inserted and removed.

A total IgE test in which a high level of antibodies is detected shows that you are allergic to something. But this can’t tell you what exactly it is you are allergic to. The specific IgE test can help pinpoint particular allergens you are testing against.

Your doctor may also recommend that you do an elimination diet to work out what exactly is responsible for your symptoms. They might do this after skin and blood tests or separately. You may be asked to follow a diet that excludes all suspected allergens to see if your symptoms abate. This method lasts for 2–4 weeks and is done under the close supervision of a doctor. Your doctor may reintroduce one food at a time to see if this causes symptoms to arise again, pinning down the ones that are to blame for the allergic reactions.12

Remember, if you try this method unsupervised at home by trial and error, you may not balance your nutritional intake and it may not even be safe. You may also miss some signs of an allergy that the doctor can spot. Which is why organizations like the Food Allergy Research and Education warn against doing this unsupervised.

An Oral Food Challenge Is A Slightly More Risky Test

An oral food challenge is usually taken up if the skin and blood tests or elimination diet you undertook were not conclusive enough. While it is a more precise and definitive test, it is also the trickiest of all methods to test for a food allergy because it is done by actually giving you a food that you may be allergic to in increasing doses. If your reaction is serious, you may need urgent medical attention. Which is why it is only done with a doctor who follows prescribed guidelines and standards laid down by the medical community for such challenges.13 14

Once you are diagnosed, your doctor may suggest that you draw up a meal plan with a nutritionist, especially if you have allergies that will need you to avoid major food groups like dairy and eggs. If you are severely allergic and at risk of anaphylactic shock, you will have to take extra precautions and may be required to carry emergency epinephrine treatment with you always.15

References   [ + ]

1, 2. Facts and Statistics. Food Allergy Research and Education.
3. Food allergy. National Health Service.
4. Food allergy. Australasian Society of Clinical Immunology and Allergy.
5. Food Allergy. U.S. National Library of Medicine.
6. Diagnosis and Testing. Food Allergy Research and Education.
7. Food Allergy Testing. American College of Allergy, Asthma & Immunology.
8, 9. Skin Prick Tests. Food Allergy Research and Education.
10. Blood Tests. Food Allergy Research and Education.
11, 15. Allergy Blood Test. U.S. National Library of Medicine.
12. Food Elimination Diet. Food Allergy Research and Education.
13. Oral Food Challenge. Food Allergy Research and Education.
14. WHAT DO PATIENTS AND CAREGIVERS NEED TO KNOW ABOUT ORAL FOOD CHALLENGES?. American Academy of Allergy, Asthma & Immunology.

Disclaimer: The content is purely informative and educational in nature and should not be construed as medical advice. Please use the content only in consultation with an appropriate certified medical or healthcare professional.