Updated 17th April 2024

Common food intolerances explained

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You can have an intolerance to any food or ingredient, but there are some common culprits, like histamines and lactose.

If you have a food intolerance, you have digestive issues after eating certain foods. The symptoms might include gas, bloating, abdominal discomfort, nausea, diarrhea, and constipation.

Some food intolerances result from a shortage of an enzyme that your body needs to break down the food. This is true for people with a lactose intolerance.

Other intolerances may be genetic or linked to certain health issues, like irritable bowel syndrome (IBS).

Determining whether you have an intolerance can be difficult. Many unvalidated at-home tests are available, but experts agree that these aren’t worth your money.

An elimination diet is the only effective way to identify a food intolerance. The diet involves not eating certain likely suspects and seeing if your symptoms go away.

Below, we describe three common food intolerances and how to handle them.

1. Lactose

About 65% of people in the world have a lactose intolerance.

Lactose is a sugar in human and animal milk. Your body uses the enzyme lactase to break down this sugar. 

Baby humans and animals produce the enzyme to digest breast milk. Most produce less and less over time as they stop drinking breast milk.

Many people don’t have enough lactase, so they can’t digest the lactose in milk.

If you have a lactose intolerance and you drink milk or eat dairy —  like ice cream, cheese, or yogurt — you may have gas, bloating, or diarrhea afterward.

These symptoms develop as the microbes in your gut begin to ferment and break down the lactose, creating gas.

Different people with the intolerance can handle different amounts of lactose. For instance, some people may be able to eat yogurt without having any symptoms.

If you want to learn more about lactose intolerance, you can listen to the ZOE Science & Nutrition podcast on the topic.


FODMAP stands for fermentable oligosaccharides, disaccharides, monosaccharides, and polyols. These are short-chain carbohydrates that are difficult for some people to digest.

If you have IBS or a condition called small intestinal bacteria overgrowth, also known as SIBO, your body doesn’t digest these carbs properly. It can cause gas, bloating, and abdominal pain.

FODMAPs are in a variety of foods, including some fruits, vegetables, beans, legumes, and grains.

We’ve taken a look at FODMAPs and the FODMAP diet in another article. It describes what to eat and what to avoid.

Many people who think they have a gluten intolerance actually have a fructan intolerance, which is a FODMAP issue.

Gluten exists in wheat, rye, and barley. But some people only have symptoms after eating wheat. In this case, the issue is the fructan in the wheat. 

Many people with a FODMAP intolerance can handle some amount of these carbs.

A registered dietitian can help figure out what’s safe to eat — and with careful guidance, it’s often possible to reintroduce FODMAPs into your diet. 

3. Histamine

Histamine is a compound involved in many of your body’s functions, including your immune response and digestion.

An enzyme called diamine oxidase (DAO) metabolizes histamine. And if you have a shortage of DAO, you may not be able to metabolize enough histamine in your gut. This can lead to high levels of histamine and an intolerance.

Having too much histamine can overload your body’s histamine receptors, leading to digestive side effects, like bloating, abdominal pain, diarrhea, and constipation. 

A histamine intolerance may also cause symptoms like those of a food allergy — a runny nose, hives, or a rapid heart rate after eating, for example. 

Microbes in your gut produce histamine after breaking down foods that contain histidine, an amino acid. 

Foods that contain the most histidine include:

  • fish

  • fermented foods, including alcohol and vinegar

  • spinach

  • eggplants

  • tomatoes

  • avocados

The only way to know if you’ve got a histamine intolerance is to eliminate these foods from your diet and track how you feel. 

If you have low levels of DAO, you could also have a histamine deficiency. DAO is available in supplement form, but it’s very expensive. A cheaper way to take in more DAO is to eat sprouted peas or legumes. 

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How is an intolerance different from an allergy?

A food intolerance is a response from your digestive system. It causes symptoms like bloating, cramps, diarrhea, and nausea.

There are different levels of intolerance. One person with a lactose intolerance may be able to handle some lactose, while another person can’t have any without experiencing symptoms. 

A food allergy is a response from your immune system. Your body reacts to the food as a threat, and this triggers an inflammatory response.

Allergic reactions can cause a runny nose, hives, and swelling of the tongue or throat, for example. Even a small amount of an allergen can cause a reaction that might be life-threatening.

Food sensitivities also result from your immune system’s inflammatory response. A sensitivity may cause stomach pain, diarrhea, joint pain, headaches, and hives. 

Unlike food allergies, food sensitivities aren’t life-threatening.

Editor’s summary

Food intolerances stem from your digestive system — while food allergies and sensitivities involve a response from your immune system.

Also, food intolerances have different levels of severity, so you may be able to have some of the triggering food without any symptoms. But if you have a food allergy, even a small amount can cause a reaction.

Testing for food intolerance

Food intolerances lead to digestive symptoms like cramps, diarrhea, nausea, or bloating. No simple test can identify an intolerance. 

The best approach is an elimination diet. It involves temporarily giving up the food or foods that are likely causing trouble and seeing if your symptoms go away. It’s best to do this under the guidance of a healthcare professional. 

Do at-home tests work?

Different at-home tests claim that they can identify food intolerances. Dr. Will Bulsiewicz, a board-certified gastroenterologist and ZOE’s U.S. medical director, says that they aren’t worth the money:

“They have not been clinically validated. And my experience is that they actually create more confusion … I don't think they're worth it.”

Managing a food intolerance

The first step is to identify the food that’s causing your symptoms.

A healthcare professional can help you develop an elimination diet that will single out the trigger. Then, you’ll reintroduce foods gradually. Together, you can find a healthy, balanced diet that’s right for your biology. 

It’s important to confirm that your issues stem from an intolerance, rather than a health condition that requires different treatment.

Another approach involves your gut microbiome. 

The community of bacteria and other microorganisms in the gut may play an important role in food intolerances. According to Dr. B, the cause of many food intolerances relates to “an alteration or disturbance of the gut microbiome and perhaps some other associated factors.”

While this is still an emerging area of research, optimizing your gut health could help if you’re living with a food intolerance. It involves eating a variety of plant foods to support the different microbes in your gut microbiome. 

We each have a unique gut microbiome, so no single approach works for everyone. Finding the right foods for you and your gut bacteria is a great way to start boosting your gut health.

ZOE’s simple at-home test can reveal your blood sugar and blood fat levels, as well as the health of your gut microbiome. Our personalized nutrition program can then help you pick the best foods for you.

Find out how it works by taking our free quiz.

Frequently asked questions

Below, we shed light on some common concerns. 

Can you get rid of a food intolerance?

You can overcome a food intolerance by adjusting your diet. First, you eliminate the trigger food, then gradually reintroduce small amounts of it into your diet.

Also, eating a diverse array of plant foods can help heal your gut, and this may help with a food intolerance.

Can you develop food intolerances in later life?

Yes, you can develop a food intolerance at any time.

Why do I have so many food sensitivities?

Many factors play into the development of food sensitivities, like your family and medical histories, your diet, and certain lifestyle elements.

Food sensitivities are different from food intolerances, but it’s possible to have a number of each. 


Food intolerances are common among adults, and they often lead to digestive symptoms. We commonly have intolerances to lactose, FODMAPs, and histamine. 

A food intolerance is different from an allergy. An intolerance triggers a digestive response, while an allergy or a sensitivity triggers an immune response.

Most people can improve their tolerance by following an elimination diet, then gradually reintroducing small amounts of the triggering food.


High and low FODMAP foods. (n.d.). http://www.monashfodmap.com/about-fodmap-and-ibs/high-and-low-fodmap-foods/ 

Histamine intolerance originates in the gut. Nutrients. (2021). https://www.mdpi.com/2072-6643/13/4/1262

Histamine intolerance: The current state of the art. Biomolecules. (2020). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7463562/ 

Lactose digestion in humans: Intestinal lactase appears to be constitutive whereas the colonic microbiome is adaptable. The American Journal of Clinical Nutrition. (2019). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6669050/ 

Lactose intolerance. StatPearls. (2023). https://www.ncbi.nlm.nih.gov/books/NBK532285/

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