Food Intolerance: Causes, Symptoms, and Treatment
Medically reviewed by Harsha Moole, MD, Internal Medicine. Last reviewed: October 23, 2026.
What kind of doctor treats Food Intolerance?
A primary care doctor can usually start the evaluation of a food intolerance. A dietitian, a food and nutrition expert, can help find trigger foods. A gastroenterologist, a doctor who treats the digestive system, may also help. A direct primary care or concierge doctor can be a first stop for an evaluation and can refer you to a specialist when needed.
What is food intolerance?
A food intolerance is when you have difficulty digesting certain foods or ingredients in food. It is not usually serious, but eating the food you are intolerant to can make you feel unwell. A food intolerance is different from a food allergy. A food allergy causes symptoms such as itchy skin, wheezing, or swelling of the lips, face and eyes.
Symptoms
Symptoms usually start a few hours after you eat the food. Common symptoms include:
- Diarrhea.
- Bloating.
- Gas.
- Belly pain.
Other symptoms can include headache, tiredness, nausea, constipation, joint pain, or rashes. Symptoms can last for a few hours or days.
Causes and who gets it
Your body cannot digest a certain food or an ingredient in food. The most common food intolerance is lactose intolerance. Lactose is a type of sugar mainly found in milk and dairy products such as cheese and yogurt. You can be intolerant to any food or ingredient, such as gluten, caffeine, or alcohol.
Unlike an allergy, an intolerance is not caused by your immune system overreacting to food. This means an intolerance does not cause a serious allergic reaction. If you ever get the warning signs under When to see a doctor, treat it as an allergy emergency.
In lactose intolerance, the small intestine makes too little lactase, the enzyme that breaks down lactose. The extra lactose passes into your colon, where bacteria break it down and create fluid and gas. Damage to the small intestine from Crohn's disease or celiac disease can also cause it.
How doctors diagnose it
A doctor may ask you to avoid the food you might be intolerant to. After a few weeks you start eating the food again to see if your symptoms return. You may be asked to keep a food and symptoms diary to find your triggers.
Other tests can include blood tests. A breath test may be used if you might be lactose intolerant. Tests you can buy that claim to diagnose food intolerances are not recommended. There is limited proof that they are accurate. They may tell you to avoid many foods, which can be harmful.
Treatment
Try to avoid or eat less of the food you are intolerant to. Do not cut foods out of your or your child's diet without advice from a doctor or dietitian. You could miss out on vitamins and minerals, which children need to grow.
For lactose intolerance, some people can have a limited amount of dairy without symptoms. Other people may need to avoid lactose altogether. Taking a supplement that contains lactase may also help. If the cause of an injured small intestine is treated, you may be able to tolerate lactose again.
When to see a doctor
See a doctor if symptoms keep coming back. Call 911 or go to the emergency room if your lips, mouth, throat or tongue suddenly become swollen. Also get emergency help if you are struggling to breathe. Get emergency help too if your throat feels tight. Get emergency help too if your skin, tongue or lips turn blue, grey or pale. Do the same if you suddenly become very confused, drowsy or dizzy. These can be signs of a serious allergic reaction.
How a direct primary care or concierge doctor fits in
A direct primary care doctor charges a flat monthly fee instead of billing insurance, while a concierge doctor usually charges more and often works alongside insurance. Either can review your symptoms and food diary, and refer you to a dietitian.
Common questions
Is a food intolerance the same as a food allergy?
No, a food intolerance is different from a food allergy. An intolerance is not caused by your immune system overreacting to food. Lactose intolerance causes uncomfortable symptoms, while a serious allergic reaction can be life threatening.
What is the most common food intolerance?
The most common food intolerance is lactose intolerance. It happens when your body cannot digest lactose, a sugar found in milk and dairy products.
Do home tests for food intolerance work?
Home tests that claim to find food intolerances are not recommended. There is limited evidence that they give accurate results.
Can I just stop eating foods that bother me?
You can avoid foods you are intolerant to, but check with a doctor or dietitian first.
How long do food intolerance symptoms last?
Symptoms can last for a few hours or days. They usually start a few hours after eating the food.
Sources
- NHS - Food intolerance
- National Institute of Diabetes and Digestive and Kidney Diseases - Symptoms & Causes of Lactose Intolerance
- MedlinePlus - Lactose Tolerance Tests
Medical Disclaimer
This content is for general educational and informational purposes only and is not medical advice. It is not a substitute for professional medical advice, diagnosis, or treatment, and reading it does not create a doctor-patient relationship. Always seek the advice of your physician or another qualified health provider with any questions about a medical condition, and never disregard or delay seeking professional advice because of something you read here. If you think you may have a medical emergency, call 911 (or your local emergency number) immediately.
