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Food allergy or intolerance: What’s the difference?

Food allergy and food intolerance are alike in some ways. But in crucial, even potentially life-threatening ways, their differences are huge.

That's why it's important for you to know which ailment you have if you have problems tolerating certain foods. If you do have a food allergy, it's vital that you take steps to avoid a reaction.

Intolerance vs. allergy

Food intolerance is a digestive system problem, according to the American Academy of Allergy, Asthma & Immunology (AAAAI). People with this condition are unable to break down certain kinds of foods.

Common examples include:

  • Lactose intolerance, which occurs when a person can't digest milk and some milk products.
  • Gluten intolerance, which happens when the body can't break down gluten—a substance found in wheat, barley and rye.
  • Intolerance of food additives such as monosodium glutamate (MSG).

People with food intolerance may experience bloating, abdominal pain or diarrhea when they eat the food that's a problem for them. Often, though, small amounts of the food will not cause symptoms, according to the AAAAI.

Food allergy is very different from food intolerance. First, it's not a digestive problem at all, but one involving the immune system.

With a food allergy, the body mistakenly identifies a protein in a particular food as a foreign invader—and the immune system attacks. This immune system response results in a sudden release of chemicals, such as histamine, that cause an allergic reaction.

A serious allergic reaction can cause wheezing, trouble breathing, a loss of consciousness and even death.

More commonly, signs of an allergic reaction appear on the skin, according to the AAAAI. They can include a rash, hives, itchiness and swelling.

Some food allergy symptoms can mimic those of food intolerance, such as diarrhea, vomiting, stomach cramps and nausea.

Among children, the most common food allergens are cow's milk, eggs and peanuts, according to the American College of Allergy, Asthma and Immunology. Among adults, the most common are fish, shellfish, peanuts and tree nuts.

People at greater risk for a food allergy are those who come from families where allergies—to food or other substances—are common. If both parents have allergies, the risk is greater than if only one parent does.

Diagnosing the problem

Without testing, it can be difficult to tell the difference between food allergy and intolerance. According to the National Institute of Allergy and Infectious Diseases, your doctor may start the diagnosis process by conducting a medical history, having you keep a food diary and having you eliminate from your diet the food that is suspected of causing a problem.

If these tests suggest food allergy, other tests may be done, such as:

  • An allergy skin test. In this test, small amounts of different food extracts are placed on a person's back or arm. If a raised bump or small hive appears, an allergy is possible. Reactions are usually seen within 20 minutes or so.
  • A blood test. People with certain conditions, such as severe eczema, can't take the skin test, so a blood test is an option. This test looks for antibodies that would point to an allergy.
  • A food challenge. While in the doctor's office, the patient eats the food suspected of causing a problem to see if there's an allergic response. If there is a serious reaction, the doctor is present to provide immediate care.

Preventing an allergic reaction

If you are diagnosed with food allergy, you'll need to take steps to make sure you prevent a reaction from occurring. The only way to do this is to strictly avoid the problem food, according to Food Allergy Research & Education. If there is an accidental exposure, medications can be given to control symptoms.

To control a severe reaction, an immediate injection of epinephrine is required. People with severe allergies may get a prescription from their doctor to carry this medicine with them, along with instructions on how to inject themselves.

If you think you or your child may have a food allergy, talk to your doctor. Finding out for sure and taking the right precautions can help prevent serious problems.

Reviewed 7/13/2023

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