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Food allergy vs. food intolerance: what's the difference?

Medically reviewed on January 9, 2022 by Jordan Stachel, M.S., RDN, CPT. To give you technically accurate, evidence-based information, content published on the Everlywell blog is reviewed by credentialed professionals with expertise in medical and bioscience fields.

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Food allergies and food intolerance are surprisingly common. The two have overlapping symptoms, making it difficult to discern between intolerance and a true allergy. Many people mistakenly lump them together, but understanding the differences can help to treat and manage symptoms. If you are looking to learn about the differences between a food allergy vs. a food intolerance, you have come to the right place. Learn more about the differences below.

What Is a Food Allergy?

Like other types of allergies, food allergies are serious conditions that are reported to affect 32 million Americans. The immune system’s job is to target foreign invaders of the body, such as bacteria or viruses, and destroy them. When someone has a food allergy, the immune system mistakenly identifies that food protein as a foreign invader, causing mild or severe symptoms to occur. In the United States, the most common food allergens include egg, fish, milk, tree nuts, nuts, wheat, soy and shellfish; however, depending on the person, the immune system can react negatively to any food [1].

Common Symptoms of a Food Allergy

Food allergies can manifest in a variety of ways. Although diarrhea and other digestive symptoms aren’t unheard of, food allergies typically result in a rapid reaction known as anaphylaxis. This most commonly comprises:

  • A rash or hives
  • Swelling in the tongue, lips, and/or throat
  • Breathing problems [2]

In its most severe forms, anaphylaxis can dramatically drop blood pressure and restrict airways. Left untreated, the adverse reaction can potentially be fatal.

Symptoms of a food allergy can occur within minutes of exposure to the food components. Unlike food intolerances, food allergies don’t actually require the food allergen to be eaten by the affected person. Simply inhaling particles or touching the food may be enough to trigger an allergic reaction [3].

What Is a Food Intolerance?

A food intolerance, on the other hand, is not related to the immune system. Instead, food intolerance is rooted in the gastrointestinal system and the enzymes used by the body to break down various food components [3]. For example, someone may lack a properly functioning lactase enzyme to effectively break down lactose, a sugar that’s often found in milk and other dairy products. As a result, that person may experience lactose intolerance. In some people, stress and psychological factors may contribute to food intolerance, though more research is necessary to understand the connection [3].

Food intolerances are much more common than food allergies, with estimates indicating that up to 15–20% of the population has a food intolerance of some kind [4].

Symptoms of Food Intolerance

As food intolerance primarily involves your digestive system, the symptoms affect your digestion. Most commonly, food intolerance can result in:

  • Cramping, gas, bloating
  • Nausea
  • Diarrhea
  • Abdominal pain
  • Vomiting
  • Heartburn
  • Indigestion [5]

Telling the Difference Between Allergy and Intolerance

The severity of the symptoms is one of the most significant differences between food allergies and food intolerances. Food intolerance can be uncomfortable, but it rarely presents with life-threatening symptoms. However, food allergies can be potentially fatal if not treated.

Many people with food intolerances can have small amounts of the specific food without triggering any symptoms. For example, someone with lactose intolerance may be able to drink a splash of cream in their coffee without suffering any reactions [5].

With food allergies, even very small amounts of the trigger food can lead to an allergic reaction, and that adverse reaction may happen every time the food is consumed.

The only way to truly know if you have a food intolerance or allergy is to work with your healthcare provider (or relevant specialist, such as an allergist) to get tested. From there, depending on the outcome of the tests, your healthcare provider may have recommendations to help keep you safe and manage potential symptoms.

If you're interested in learning more about your body's reactions to food in ways unrelated to allergies or intolerances, consider a food sensitivity test.

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1. What Is a Food Allergy? Food Allergy Research & Education. URL. Accessed January 9, 2022.

2. Food Allergy vs. Intolerance: What’s the Difference? Cleveland Clinic. URL. Accessed January 9, 2022.

3. Food Intolerance Versus Food Allergy. American Academy of Allergy, Asthma & Immunology. URL. Accessed January 9, 2022.

4. Lomer MC. Review article: the aetiology, diagnosis, mechanisms and clinical evidence for food intolerance. Aliment Pharmacol Ther. 2015 Feb;41(3):262-75. PMID: 25471897.

5. Food Problems: Is it an Allergy or Intolerance. Cleveland Clinic. URL. Accessed January 9, 2022.

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