Food Intolerance or Allergy? Your Guide to Common Intolerances

Medically Reviewed By Jerlyn Jones, MS MPA RDN LD CLT
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If you have a food intolerance, you will experience adverse reactions to eating certain foods, such as food containing lactose or gluten. An inability to digest these foods can result in symptoms including bloating, diarrhea, and gas. Food intolerance is different from a food allergy, as it does not involve the immune system. Intolerance will typically only occur if you eat a substantial amount of the specific food, and symptoms tend to happen gradually over a few hours.

Read on to find out about common food intolerances. This guide also includes information about diagnosis and prevention.

Food intolerance definition

Food intolerance occurs when you are unable to properly digest certain foods. Once you consume a substantial amount of the food, symptoms such as bloating and diarrhea will gradually begin over a few hours.

Unlike a food allergy, food intolerance is not life threatening.

Food intolerance vs. food allergy

There is a closeup of two ice cream cones.
Jamie Grill Atlas/Stocksy United

The table below highlights some important differences between food intolerance and food allergy.

Food intoleranceFood allergy
Food intolerance is a chemical reaction to certain foods.Food allergy is a reaction by your immune system.
You will usually need to consume a substantial amount of the food for symptoms of intolerance to happen.You may only need to encounter traces of the food for an allergic reaction to happen.
Symptoms occur gradually over the course of a few hours.Symptoms can occur suddenly and progress rapidly.
Symptoms include bloating, diarrhea, and gas.Life threatening symptoms include swelling, breathing difficulties, and anaphylaxis.
Symptoms of food intolerance typically affect the digestive system.An allergic reaction can affect different body parts.
You can be intolerant to many different foods.Allergies tend to be toward specific foods.
Common food intolerances include lactose, gluten, and caffeine.Common food allergies include fish and nuts.

Learn more about food allergies.

What are some common food intolerances?

Foods that commonly cause intolerances include:

  • gluten
  • dairy products
  • caffeine
  • chocolate
  • some fruits and vegetables, such as:
    • strawberries
    • citrus fruit
    • tomatoes
  • egg white
  • food additives and flavor enhancers, including monosodium glutamate (MSG)
  • foods containing histamine

What are the symptoms of food intolerance?

Symptoms of food intolerance include:

Food intolerance symptoms typically occur within a few hours after eating the food. In some cases, they may take 12–24 hours to occur.

The severity of symptoms will depend on the amount of food consumed. Each person will have a different tolerance or threshold level for how much of a certain food they can eat before they experience symptoms of intolerance.

What causes food intolerance?

Medical professionals do not always know what causes a person to become sensitive to certain foods.

Symptoms may occur when your body cannot digest certain foods, which can happen due to insufficient enzymes.

This can also result from a metabolic condition, including lactose intolerance. These are genetic conditions where your body cannot metabolize certain foods properly.

Pharmacological food intolerance occurs when your body is sensitive to certain chemicals or food components, including:

When should I contact a doctor?

Contact your doctor if you experience symptoms of food intolerance. They will help you begin cutting out possible triggers from your diet and help you to monitor your symptoms.

Seek immediate medical advice if you experience a severe allergic reaction or anaphylaxis.

Anaphylaxis is a severe reaction to a trigger, such as an allergy, and is potentially life threatening. 

Symptoms can come on quickly and include: 

If you or someone around you develops these symptoms, you should: 

  1. Check to see whether they have an epinephrine pen. If they do, read and follow the instructions to dispense the medication.
  2. Dial 911 (or a local emergency number).
  3. Lay them down. If they have vomited, lay them on their side. 
  4. Stay with them until emergency services arrive. 

It is possible for someone to need more than one injection with an epinephrine pen. If symptoms do not begin to clear after 5 minutes, give a second injection if one is available.

Is there a food intolerance test?

Some experts believe that are no reliable tests for food intolerance.

Some laboratories have produced tests with claims that they can test for food intolerances at home. However, the Food and Drug Administration (FDA) has not approved these tests.

Some medical professionals will use a hydrogen breath test for lactose intolerance. This noninvasive test may help with diagnosing lactose intolerance.

Contact your doctor if you have concerns about food intolerance. They will be able to advise on how best to manage your symptoms and monitor your diet to identify possible triggers.

How is food intolerance diagnosed?

It can be difficult to diagnose food intolerance, as other conditions can cause similar symptoms. If you present with symptoms of food intolerance, your doctor may carry out tests to rule out the following conditions:

If your doctor suspects you have an intolerance to a certain food, they will advise you to remove this food from your diet and monitor your symptoms. They will ask you to keep a log or diary, which should include information such as:

  • what you eat
  • any symptoms you experience
  • when you experience these symptoms

Your doctor may ask you to reintroduce the food into your diet to see if your symptoms begin again or worsen. You may need to gradually begin eating the food again to find out if you can tolerate it in smaller amounts.

As you may have an intolerance to more than one food, this can be a process of trial-and-error. You may need to remove certain foods from your diet for 2–6 weeks.

How is food intolerance treated?

The best way to treat food intolerance is to remove any known triggers from your diet. You may be able to gradually reintroduce the food back into your diet, as you may be able to tolerate it in smaller amounts.

You can also prevent symptoms from occurring by making sure you thoroughly read food labels to check for ingredients. The FDA ensures that prepared foods for sale in the United States are properly labeled.

Lactose intolerance foods to avoid

Around 65% of people have lactose intolerance. It typically begins in adolescence or early adulthood.

Foods to avoid if you are lactose intolerant include:

  • cheese
  • milk and cream
  • ice cream
  • sour cream
  • whey
  • pancakes and waffles
  • butter and margarine
  • custard
  • pudding

You should avoid any food that contains milk or dairy. This includes foods such as mashed potatoes made with milk, desserts that contain cream, and dairy yogurts.

Learn more about lactose intolerance.

Fructose intolerance foods to avoid

You can find fructose in both natural and processed foods. Try to avoid foods that are high in fructose.

Fruits high in fructose include:

  • apples
  • dried fruits
  • grapes
  • kiwi
  • lychee
  • pears
  • mango
  • prunes
  • watermelon

Vegetables and vegetable products high in fructose include:

  • tomato ketchup
  • pickles
  • sweet corn
  • sugar snap peas
  • tomato sauce

Other foods high in fructose include:

  • honey, syrups, and other sweeteners
  • chocolate
  • ice cream
  • candy
  • cookies
  • cake

Gluten intolerance foods to avoid

Reading product labels can help you identify foods that contain gluten.

Examples of foods to avoid if you have a gluten intolerance include:

  • cereals
  • pasta
  • bread
  • crackers
  • cookies
  • cakes
  • pies
  • pastries
  • gravies

Some grocery stores offer gluten-free options for some of these foods. Always check the labels before consuming anything that might contain gluten if you have an intolerance.

Learn more about gluten sensitivity.

Is celiac disease the same as food intolerance?

Celiac disease affects around 1% of people in the U.S. It is a chronic immune condition rather than an intolerance. However, celiac disease may share symptoms with gluten intolerance.

Symptoms of celiac disease include:

As celiac disease damages the small intestines, this can result in some people becoming lactose intolerant.

Around 6% of people in the U.S. have a condition known as “nonceliac gluten sensitivity.” This means that they may have a gluten intolerance. However, it is not due to an immune condition such as celiac disease.

Find out more about celiac disease.

Summary

Food intolerance occurs when your body cannot properly digest certain foods. Examples include food containing lactose, glucose, or fructose.

Treatment for food intolerance focuses on removing triggers from your diet. Your doctor may ask you to keep a food diary as you remove and reintroduce certain foods into your diet.

Contact your doctor if you have concerns about food intolerance. They will help you identify which foods may be causing symptoms such as bloating, diarrhea, and gas.

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Medical Reviewer: Jerlyn Jones, MS MPA RDN LD CLT
Last Review Date: 2022 Jun 29
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THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.