Blog Post

December 6, 2022

Do You Know the Difference Between a Food Allergy and a Food Intolerance?

Food allergies and food intolerances are not the same things. While food allergies affect around 10% of adults and children in the United States,  there is confusion about what constitutes an allergy or intolerance. For example, they talk about having a food allergy when they have  a food intolerance and vice-versa. Let's look at the difference between the two terms.

Allergic Food Reactions Come on Quickly and Involve the Immune System

A food allergy is an immune response to a specific food. It can range from mild reactions like hives or upset stomach to severe reactions like anaphylaxis, which may be life-threatening and require medical attention.

Food intolerances are not immune-related responses but rather symptoms of digestive distress caused by a particular food or ingredient that you're sensitive to or intolerant of. Unlike allergies, they don't involve the immune system. In the case of food  intolerance, your body can't process the offending substance in your gut due to something like low stomach acidity, enzyme deficiency, or some other non-immune-mediated reason.

Food intolerances are usually not as severe as a true allergic reaction. They also don't happen immediately after consuming an offending food. The response can be delayed by hours, even up to a day or so. Still, food intolerances can have serious health consequences. For example, they can lead to weight loss due to poor absorption of nutrients or cause unpleasant symptoms like gas and bloating from incomplete food breakdown. They can also exacerbate conditions like acid reflux.

Food Intolerance Is Harder to Diagnose

The symptoms of a food intolerance are often hard to pinpoint. Some people attribute them to an underlying health problem and repeatedly seek medical attention to no avail. It can take months or years to realize that the symptoms are coming from a food intolerance.

Specific Types of Allergies and Food Intolerances

A classic example of a food allergy is an allergy to peanuts, which is common in children. When someone with a peanut allergy eats a peanut, their body views the peanut as a foreign invader and releases chemicals to try and fight it off. This causes the person's airways to constrict, leading to difficulty breathing. Their heart rate increases, and their blood pressure may drop. In severe cases, this can lead to anaphylactic shock, a complication that can lead to death.

One of the most common food intolerances is lactose intolerance, which affects almost 65% of the adult population to some degree. Symptoms of lactose intolerance usually start within 30 minutes to two hours after consuming dairy. The severity of the symptoms depends on the individual and the amount of the offending food.  Common symptoms include nausea, cramps, diarrhea, bloating, and gas. In severe cases, vomiting may also occur.

Lactose intolerance is caused by a deficiency of the enzyme lactase, which your gut needs to break down lactose, a sugar in milk and other dairy products. When lactose isn't broken down, it travels to the large intestine, where bacteria ferment it, leading to the production of gas and other symptoms.

The Symptoms of Food Allergies and Intolerances May Differ

Symptoms of both allergies and intolerances vary widely, from mild to severe.

Food allergy symptoms vary and can be severe, including anaphylaxis. With food intolerance, digestive issues are common. The most common symptoms of food intolerance are gas, bloating, abdominal cramping, headaches, heartburn, and nausea.

Food allergy symptoms vary but can include hives, swelling of the lips and mouth or throat, tingling in the mouth and tongue, and lightheadedness. Severe allergic reactions to a food can lead to loss of consciousness or  death. That's why people with allergies should carry an epinephrine pen (prescribed by a doctor), which can be lifesaving if such a reaction occurs. Talk to your physician about this.

Diagnosing Food Allergies and Food Intolerances

There are key differences in how food allergies and intolerances are diagnosed. First, food allergies are diagnosed by testing for specific  antibodies to the offending food through blood tests and skin prick tests. An allergist can run these tests for you.

On the other hand, Intolerances are typically diagnosed by keeping a food diary and looking for patterns of symptoms after eating certain foods.

To keep a food diary, start by downloading a food tracking app or keeping a physical journal. Next, record everything you eat and drink throughout the day, including the time and amount. Be sure to include any snacks or additional beverages. Finally, review your entries at the end of the day and note  any patterns.

Another approach for identifying food intolerances is to do an elimination diet. An elimination diet is a short-term diet that eliminates certain foods from your diet to identify food sensitivities.

It is best to work with a healthcare professional when doing an elimination diet, as they can help you identify  which foods to eliminate and how to do so safely and healthily. After eliminating possible foods you're intolerant to, you gradually reintroduce the eliminated foods one at a time to see how your body reacts.


Food allergies and intolerances are both common conditions that can cause discomfort. If you think you have an intolerance or allergy to something, it's important to talk to your doctor about how to  manage it.


Ortolani C, Pastorello EA. Food allergies and food intolerances. Best Pract Res Clin Gastroenterol. 2006;20(3):467-83. doi: 10.1016/j.bpg.2005.11.010. PMID: 16782524.

"Food allergy - Symptoms and causes - Mayo Clinic." 31 Dec. 2021,

"Food Intolerance Versus Food Allergy - American Academy of Allergy ...." 28 Sept. 2020,

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