Unlike some allergies, food intolerances aren't life-threatening. However, they can be very problematic for those affected.

Food intolerances and sensitivities are extremely common and seem to be on the rise (1).

In fact, it’s estimated that up to 20% of the world’s population may have a food intolerance (2).

Food intolerances and sensitivities can be hard to diagnose due to their wide range of symptoms.

This article reviews the most common types of food sensitivities and intolerances, their related symptoms and foods to avoid.

Cappuccino Close-up

The term “food hypersensitivity” refers to both food allergies and food intolerances (3).

A food intolerance is not the same as a food allergy, although some of the symptoms may be similar.

In fact, it can be difficult to tell food allergies and food intolerances apart, making it important to speak with your doctor if you suspect you might have an intolerance.

When you have a food intolerance, symptoms usually begin within a few hours of eating the food that you are intolerant to.

Yet, symptoms can be delayed by up to 48 hours and last for hours or even days, making the offending food especially difficult to pinpoint (4).

What’s more, if you frequently consume foods that you are intolerant to, it may be difficult to correlate symptoms to a specific food.

While symptoms of food intolerances vary, they most often involve the digestive system, skin and respiratory system.

Common symptoms include (5):

  • Diarrhea
  • Bloating
  • Rashes
  • Headaches
  • Nausea
  • Fatigue
  • Abdominal pain
  • Runny nose
  • Reflux
  • Flushing of the skin

Food intolerances are commonly diagnosed by elimination diets specifically designed to narrow down offending foods or through other testing methods.

Elimination diets remove foods most commonly associated with intolerances for a period of time until symptoms subside. Foods are then reintroduced one at a time while monitoring for symptoms (6).

This type of diet helps people identify which food or foods are causing symptoms.

Here are 8 of the most common food intolerances.

Lactose is a sugar found in milk and dairy products.

It is broken down in the body by an enzyme called lactase, which is necessary in order for lactose to be properly digested and absorbed.

Lactose intolerance is caused by a shortage of lactase enzymes, which causes an inability to digest lactose and results in digestive symptoms.

Symptoms of lactose intolerance include (7):

  • Abdominal pain
  • Bloating
  • Diarrhea
  • Gas
  • Nausea

Lactose intolerance is extremely common.

In fact, it is estimated that 65% of the world’s population has trouble digesting lactose (8).

Intolerance can be diagnosed several ways, including a lactose-tolerance test, lactose breath test or stool PH test.

If you think you may have an intolerance to lactose, avoid dairy products that contain lactose, such as milk and ice cream.

Aged cheeses and fermented products like kefir may be easier for those with lactose intolerance to tolerate, as they contain less lactose than other dairy products (9).

Summary Lactose intolerance is common and involves digestive symptoms including diarrhea, bloating and gas. People with lactose intolerance should avoid dairy products like milk and ice cream.

Gluten is the general name given to proteins found in wheat, barley, rye and triticale.

Several conditions relate to gluten, including celiac disease, non-celiac gluten sensitivity and wheat allergy.

Celiac disease involves an immune response, which is why it is classified as an autoimmune disease (10).

When people with celiac disease are exposed to gluten, the immune system attacks the small intestine and can cause serious harm to the digestive system.

Wheat allergies are often confused with celiac disease due to their similar symptoms.

They differ in that wheat allergies generate an allergy-producing antibody to proteins in wheat, while celiac disease is caused by an abnormal immune reaction to gluten in particular (11).

However, many people experience unpleasant symptoms even when they test negative for celiac disease or a wheat allergy.

This is known as non-celiac gluten sensitivity, a milder form of gluten intolerance that has been estimated to impact anywhere from 0.5 to 13% of the population (12).

Symptoms of non-celiac gluten sensitivity are similar to those of celiac disease and include (13):

  • Bloating
  • Abdominal pain
  • Diarrhea or constipation
  • Headaches
  • Fatigue
  • Joint pain
  • Skin rash
  • Depression or anxiety
  • Anemia

Both celiac disease and non-celiac gluten sensitivity are managed with a gluten-free diet.

It involves adhering to a diet free from foods and products that contain gluten, including:

  • Bread
  • Pasta
  • Cereals
  • Beer
  • Baked goods
  • Crackers
  • Sauces, dressing and gravies, especially soy sauce
Summary Gluten is a protein found in wheat, barley, rye and triticale. People with an intolerance to gluten may experience symptoms such as abdominal pain, bloating and headaches.

Caffeine is a bitter chemical that is found in a wide variety of beverages, including coffee, soda, tea and energy drinks.

It’s a stimulant, meaning it reduces fatigue and increases alertness when consumed.

It does so by blocking receptors for adenosine, a neurotransmitter that regulates the sleep-wake cycle and causes drowsiness (14).

Most adults can safely consume up to 400 mg of caffeine a day without any side effects. This is the amount of caffeine in about four cups of coffee (15).

However, some people are more sensitive to caffeine and experience reactions even after consuming a small amount.

This hypersensitivity to caffeine has been linked to genetics, as well as a decreased ability to metabolize and excrete caffeine (16).

A caffeine sensitivity is different than a caffeine allergy, which involves the immune system.

People with a hypersensitivity to caffeine may experience the following symptoms after consuming even a small amount of caffeine (17):

  • Rapid heartbeat
  • Anxiety
  • Jitters
  • Insomnia
  • Nervousness
  • Restlessness

People with a sensitivity to caffeine should minimize their intake by avoiding foods and beverages that contain caffeine, including coffee, soda, energy drinks, tea and chocolate.

Summary Caffeine is a common stimulant to which some people are hypersensitive. Even a small amount can cause anxiety, rapid heartbeat and insomnia in some individuals.

Salicylates are natural chemicals that are produced by plants as a defense against environmental stressors like insects and disease (18).

Salicylates have anti-inflammatory properties. In fact, foods rich in these compounds have been shown to protect against certain diseases like colorectal cancer (19).

These natural chemicals are found in a wide range of foods, including fruits, vegetables, teas, coffee, spices, nuts and honey.

Aside from being a natural component of many foods, salicylates are often used as a food preservative and may be found in medications.

While excessive amounts of salicylates can cause health problems, most people have no problem consuming normal amounts of salicylates found in foods.

However, some people are extremely sensitive to these compounds and develop adverse reactions when they consume even small amounts.

Symptoms of salicylate intolerance include (20):

  • Stuffy nose
  • Sinus infections
  • Nasal and sinus polyps
  • Asthma
  • Diarrhea
  • Gut inflammation (colitis)
  • Hives

While completely removing salicylates from the diet is impossible, those with a salicylate intolerance should avoid foods high in salicylates like spices, coffee, raisins and oranges, as well as cosmetics and medications that contain salicylates (20).

Summary Salicylates are chemicals found naturally in many foods and used as preservatives in foods and medications. People who are intolerant to salicylates can experience symptoms like hives, stuffy nose and diarrhea when exposed.

Amines are produced by bacteria during food storage and fermentation and found in a wide variety of foods.

Though there are many types of amines, histamine is most frequently associated with food-related intolerances.

Histamine is a chemical in the body that plays a role in the immune, digestive and nervous systems.

It helps protect the body from infection by creating an immediate inflammatory response to allergens. This triggers sneezing, itching and watery eyes in order to potentially excrete harmful invaders (21).

In people without an intolerance, histamine is easily metabolized and excreted.

However, some people are not able to break down histamine properly, causing it to build up in the body.

The most common reason for histamine intolerance is impaired function of the enzymes responsible for breaking down histamine — diamine oxidase and N-methyltransferase (22).

Symptoms of histamine intolerance include (23):

  • Flushing of the skin
  • Headaches
  • Hives
  • Itching
  • Anxiety
  • Stomach cramps
  • Diarrhea
  • Low blood pressure

People with an intolerance to histamine should avoid foods high in this natural chemical, including:

  • Fermented foods
  • Cured meats
  • Dried fruits
  • Citrus fruits
  • Avocados
  • Aged cheeses
  • Smoked fish
  • Vinegar
  • Soured foods like buttermilk
  • Fermented alcoholic beverages like beer and wine
Summary Histamine is a compound that can cause symptoms like itching, hives and stomach cramps in people who are unable to properly break down and excrete it from the body.

FODMAPs is an abbreviation that stands for fermentable oligo-, di-, mono-saccharides and polyols (24).

They are a group of short-chain carbohydrates found naturally in many foods that can cause digestive distress.

FODMAPs are poorly absorbed in the small intestine and travel to the large intestine, where they are used as fuel for the gut bacteria there.

The bacteria break down or “ferment” the FODMAPs, which produces gas and causes bloating and discomfort.

These carbohydrates also have osmotic properties, meaning they draw water into the digestive system, causing diarrhea and discomfort (25).

Symptoms of a FODMAP intolerance include (26):

  • Bloating
  • Diarrhea
  • Gas
  • Abdominal pain
  • Constipation

FODMAP intolerances are very common in people with irritable bowel syndrome, or IBS.

In fact, up to 86% of people diagnosed with IBS experience a reduction in digestive symptoms when following a low-FODMAP diet (27).

There are many foods high in FODMAPs, including:

  • Apples
  • Soft cheeses
  • Honey
  • Milk
  • Artichokes
  • Bread
  • Beans
  • Lentils
  • Beer
Summary FODMAPs are a group of short-chain carbohydrates found in a wide array foods. They can cause digestive distress in many people, especially those with IBS.

Sulfites are chemicals that are primarily used as preservatives in foods, drinks and some medications.

They can also be found naturally in some foods like grapes and aged cheeses.

Sulfites are added to foods like dried fruit to delay browning and wine to prevent spoilage caused by bacteria (28).

Most people can tolerate the sulfites found in foods and beverages, but some people are sensitive to these chemicals.

Sulfite sensitivity is most common in people with asthma, though people without asthma can be intolerant to sulfites as well.

Common symptoms of sulfite sensitivity include (29):

  • Hives
  • Swelling of the skin
  • Stuffy nose
  • Hypotension
  • Flushing
  • Diarrhea
  • Wheezing
  • Coughing

Sulfites can even cause airway constriction in asthmatic patients with sulfite sensitivity, and, in severe cases, it can lead to life-threatening reactions.

The Food and Drug Administration (FDA) mandates that the use of sulfites must be declared on the label of any food that contains sulfites or where sulfites were used during the processing of food (30).

Examples of foods that may contain sulfites include (31):

  • Dried fruit
  • Wine
  • Apple cider
  • Canned vegetables
  • Pickled foods
  • Condiments
  • Potato chips
  • Beer
  • Tea
  • Baked goods
Summary Sulfites are commonly used as preservatives and can be found naturally in certain foods. People who are hypersensitive to sulfites can experience symptoms like stuffy nose, wheezing and low blood pressure.

Fructose, which is a type of FODMAP, is a simple sugar found in fruits and vegetables, as well as sweeteners like honey, agave and high-fructose corn syrup.

The consumption of fructose, especially from sugar-sweetened beverages, has risen dramatically in the past forty years and been linked to an increase in obesity, liver disease and heart disease (32, 33).

Aside from a rise in fructose-related diseases, there has also been a surge in fructose malabsorption and intolerance.

In people with fructose intolerance, fructose isn’t efficiently absorbed into the blood (34).

Instead, the malabsorbed fructose travels to the large intestine, where it is fermented by gut bacteria, causing digestive distress.

Symptoms of fructose malabsorption include (35):

  • Reflux
  • Gas
  • Diarrhea
  • Nausea
  • Abdominal pain
  • Vomiting
  • Bloating

People with an intolerance to fructose are often also sensitive to other FODMAPs and can benefit from following a low-FODMAP diet.

In order to manage symptoms related to fructose malabsorption, the following high-fructose foods should be avoided (36):

  • Soda
  • Honey
  • Apples, apple juice and apple cider
  • Agave nectar
  • Foods containing high-fructose corn syrup
  • Certain fruits like watermelon, cherries and pears
  • Certain vegetables like sugar snap peas
Summary Fructose is a simple sugar that is malabsorbed by many people. It can cause symptoms such as bloating, gas and diarrhea in those who can’t properly absorb it.

The food intolerances listed above are among the most common types.

However, there are many other foods and ingredients to which people may be intolerant, including:

  • Aspartame: Aspartame is an artificial sweetener that is commonly used as a sugar substitute. Although research is conflicting, some studies have reported side effects like depression and irritability in people with a sensitivity (37).
  • Eggs: Some people have difficulty digesting egg whites but are not allergic to eggs. Egg intolerance is associated with symptoms like diarrhea and abdominal pain (38).
  • MSG: Monosodium glutamate, or MSG, is used as a flavor-enhancing additive in foods. More research is needed, but some studies have shown that large amounts can cause headache, hives and chest pain (39, 40).
  • Food colorings: Food colorings like Red 40 and Yellow 5 have been shown to cause hypersensitivity reactions in some people. Symptoms include hives, skin swelling and stuffy nose (41).
  • Yeast: People with a yeast intolerance generally experience less severe symptoms than those with a yeast allergy. Symptoms are typically limited to the digestive system (42).
  • Sugar alcohols: Sugar alcohols are often used as zero calorie alternatives to sugar. They can cause major digestive issues in some people, including bloating and diarrhea (43).
Summary There are many foods and food additives to which people are intolerant. Food colorings, MSG, eggs, aspartame and sugar alcohols have all been shown to cause symptoms in certain people.

Food intolerances differ from allergies. Most do not trigger the immune system, and their symptoms are usually less severe.

However, they can negatively impact your health and should be taken seriously.

Many people are intolerant or hypersensitive to foods and additives like dairy products, caffeine and gluten.

If you suspect that you may be intolerant to a certain food or food additive, speak to your doctor or dietitian about testing and treatment options.

Although food intolerances are usually less serious than food allergies, they can negatively affect your quality of life.

This is why it's important to take steps to identify food intolerances in order to prevent unwanted symptoms and health issues.