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Do You Have a Food Allergy or Intolerance? We Asked a Biochemist How To Tell the Difference

It's something you need to know.


Have you ever noticed that when you eat a certain food, your stomach hurts? Or maybe you have a favorite snack, but it always leaves you feeling sluggish? Perhaps you experience uncomfortable symptoms like joint pain and migraines, but you aren’t sure why. If any of this sounds familiar, you might have a food allergy or intolerance. That said, an allergy and an intolerance are two very different things — and knowing which one you’re experiencing is vital to receiving the right treatment. We asked an expert to define and distinguish food allergies and intolerances, so you can take control of your health.

Meet the Expert

Dr. Gill Hart is a leading biochemist and the scientific director at YorkTest Laboratories, a UK-based company that creates science-backed home testing for food allergies and intolerances. Here, she answers some of our biggest questions on the topic. 

What is a food allergy? What is a food intolerance?

Food allergy: A food allergy is defined as an immediate, potentially life-threatening severe immune reaction that you can have to eating certain foods. It is estimated that food allergies affect about 32 million people in the US, or 10 percent of the population.

Food intolerance or sensitivity: A food intolerance isn’t usually life-threatening and typically causes milder reactions that are delayed (by hours or days). Food intolerances and sensitivities affect even more people than allergies, with an estimated 45 percent of the population suffering.

Clearly, both food allergies and food intolerances are very common. Food allergies are much more severe, but food intolerances and sensitivities can also be very impactful, longer term, on your quality of life. 

How do the symptoms differ?

Food allergy: Food allergies cause immediate symptoms such as tingling lips, swelling in the mouth and airways, vomiting, stomach pains, and collapse (anaphylaxis) — and they can sometimes be fatal.

Food intolerance or sensitivity: Food intolerances cause symptoms such as irritable bowel syndrome (IBS), bloating and gas, diarrhea, and constipation. They can also cause migraines and headaches; skin symptoms such as acne, psoriasis, and hives; low energy and low mood; joint pains; sinusitis, and more. These are the sort of symptoms that are ongoing. A lot of people don’t even realize that they have a food intolerance or sensitivity, and think that their food sensitivity symptoms are “normal” for them. 

At what point should you receive medical attention for either?

Food allergy: If you suspect that you or someone you are with is having an allergic reaction to food, then medical attention should be sought immediately. (Per MayoClinic: If someone is having an allergic reaction, don’t’ wait to see if symptoms improve — seek emergency medical attention right away. While you wait for help to arrive, ask if the person suffering from the reaction has an epinephrine autoinjecter (like an EpiPen). Offer to help administer it. The person should lie down, face up, and be still. Loosen tight clothing, cover them with a blanket, and don’t give them anything to drink. If bleeding from the mouth or vomiting, turn person to the side to prevent choking.)

Food intolerance or sensitivity: If you have symptoms of food intolerance or food sensitivity, it is wise to get a medical check-up to rule out anything serious. However, many people live with chronic symptoms such as IBS, migraines, low energy, and low mood, assuming it’s “normal” and cannot be helped — when, in fact, it can be due to a food intolerance or sensitivity, and eliminating that food may be a solution. 

What are common food allergies and common intolerances?

Food allergy: The most common allergies are reactions to milk, eggs, shellfish, peanuts, tree nuts, sesame, and soy. 

Food intolerance or sensitivity: These are often associated with milk sugar (lactose) intolerance. Food sensitivities can occur with many different food types, ranging from common foods such as milk, wheat, and eggs, to other foods that people might not consider, such as fruits, vegetables, lentils, and coffee. At YorkTest, they assess reactions to over 200 different food and drink ingredients. YorkTest has shown that those who have food sensitivities, react to, on average, about five or six different food ingredients. This makes it difficult to determine which foods are causing problems, and that’s why food sensitivity testing is helpful.

Is gluten often something to which people are allergic or intolerant?

Gluten can cause several different types of problems. Gluten is associated with Celiac Disease, which is an autoimmune reaction (where the body attacks itself) triggered by gluten. Celiac Disease affects about 1 in 100 people in the US and requires medical intervention. You can also be allergic to wheat — which contains gluten — but this is relatively rare. Much more common is the condition of non-celiac gluten sensitivity (NCGS), for which YorkTest can help test.

At what age do food allergies and food intolerances develop?

Food allergy: Food allergies typically develop in childhood and then generally carry on into adulthood. But allergies can also develop in adults.

Food intolerance or sensitivity: Food intolerances can and often do develop at any age; at YorkTest, they check for food sensitivities from age two and up

Can food allergies or food intolerances go away?

Food allergy: Allergies in adulthood are usually for life, and Celiac Disease is also a lifelong condition; both must be carefully managed, and you must never ever attempt to eat a food that you know you are allergic to. You always need to check food labels and check ingredients in restaurants.

Food intolerance or sensitivity: Food sensitivities are different. Sometimes, foods can be tolerated again after a period of elimination. Occasionally, just a small amount can be tolerated after a break; it is possible, after removing a food from your diet for about three months, to slowly reintroduce it back. Gut healing is key, and a nutritional therapist can help with any dietary changes and supplements required to support that healing.

What is your opinion on at-home test kits?

With advances in science, the use of at-home test kits is becoming more and more popular. There are different types of at-home tests. The main type is where you collect a small blood sample, using the blood collection kit provided, in the comfort of your own home, and send the sample back to an accredited laboratory for testing. 

YorkTest has been offering at-home food sensitivity testing like this for over 25 years, and has strong evidence that their tests work. Of those who removed foods from the diet identified by the YorkTest Premium Food Sensitivity Test, 82 percent reported an improvement in their health and well-being. YorkTest measures all four subtypes of food-specific IgG reactions, which means that reactions aren’t missed; subtypes IgG1-3, in particular, are known to be linked to inflammation in the body, and it is not normal to have high levels of these in your blood. (Click through for more on at home food sensitivity tests)

What does treatment look like for food allergies vs. food intolerances?

Avoiding the culprit food is key for both. Try the elimination diet to figure out whether you have a particular food intolerance; cut it out of your diet for a while and see how you feel. For allergies, protective measures are vital, such as always carrying an automatic injection device containing epinephrine for emergencies. 

Food is a vital part of our daily life — we need it to live and thrive. If you suspect that you’re feeling unwell because of something you ate, it’s important to determine the problem food, and work to figure out why your body is reacting that way. Always consult your doctor for guidance.

This content is not a substitute for professional medical advice or diagnosis. Always consult your physician before pursuing any treatment plan.

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