What Are the Most Common Food Intolerances?

The three most common food intolerances are lactose, a sugar found in milk, casein, a protein found in milk, and gluten, a protein found in grains such as wheat, rye, and barley.

What is food intolerance?

Food intolerance is a condition in which a person is unable, or finds it difficult to digest certain foods, and experiences gastrointestinal disturbances when they eat such foods. Food intolerance occurs when the digestive system cannot break down certain ingredients in food. Symptoms of food intolerance primarily relate to the digestive system and are rarely dangerous.

What is a food allergy?

Food allergy is the immune system’s reaction to certain foods which it perceives as harmful. Unlike food intolerance, food allergies can cause symptoms all over the body, which can vary from mild to extremely severe. Food allergy, just like other allergies, can cause a potentially life-threatening condition known as anaphylactic shock.

Food intolerance and food allergy may often be difficult to distinguish because they have many common symptoms. Following are some general indications to know whether your reaction is food intolerance or allergy:

Food intolerance

• Symptoms are limited to digestive issues.
• Symptoms occur over a few hours after eating.
• The severity of symptoms depends on the amount of food eaten. Small amounts eaten infrequently may produce no symptoms.
• Symptoms are not life-threatening.

Food allergy

• Symptoms can involve any part of the body; skin and respiratory systems are often involved, in addition to digestive symptoms.
• Symptoms can happen immediately after eating.
• Even small amounts of the food trigger a reaction and it happens every time you eat the food.
• Symptoms can be mild or potentially life-threatening depending on which part of the body is involved and how strongly the immune system reacts.

A doctor will be able to confirm with certain tests, whether your reaction is from a food allergy. Blood tests that look for a type of antibody known as immunoglobulin E (IgE) can help diagnose if you have a food allergy, and skin prick tests with food extracts can help identify the specific food allergen.

It is more difficult to identify the specific food that you are intolerant to because it cannot be detected with a skin prick test. A hydrogen breath test can help identify some food intolerances, but most often you may have to go on an elimination diet and maintain a detailed diary of the food you eat, and the symptoms you have.

Symptoms that are common to food intolerance and food allergy include:

• Nausea
• Stomach pain
• Vomiting
• Diarrhea

Symptoms of food intolerance include:

• Gas and bloating
• Stomach cramps
• Heartburn
• Headaches
• Irritability or nervousness

Symptoms of food allergy include:

• Rash or hives anywhere in the body
• Itching
• Shortness of breath
• Chest pain
• Anaphylaxis, a medical emergency that requires an immediate 911 call. The symptoms of anaphylaxis include:
  • Difficulty breathing
  • A sudden drop in blood pressure
  • Trouble swallowing

The three most common food intolerances are:

• Lactose, a sugar found in milk
• Casein, a protein found in milk
• Gluten, a protein found in grains such as wheat, rye, and barley.

The following foods cause most food intolerances and allergies:

• Milk
• Wheat
• Nuts such as peanuts, walnuts, pecans, and almonds, which contain a substance known as a salicylate
• Eggs, particularly yolks
• Fish
• Shellfish
• Soy
• Mushrooms
• Red wine, beer, and certain foods which contain a substance known as sulfite used as a preservative
• Foods that contain an additive known as monosodium glutamate (MSG)

The common causes of food intolerance include: 

• Lack of an enzyme (enzymopathy) to digest a specific food. For instance, lactose intolerance is caused by the lack of lactase, the enzyme that breaks down lactose.
• Celiac disease, a condition caused by a gluten allergy. Celiac disease, however, does not have the risk of anaphylaxis.
• Sensitivity to food additives and preservatives.
• Gastrointestinal conditions such as irritable bowel syndrome (IBS)
• Chronic stomach infections and bacterial overgrowth

The best protection against food intolerances and allergies is to avoid the food altogether. In the case of food intolerance, after identifying and eliminating the food from your diet for a period, you may sometimes be able to slowly reintroduce the food in small quantities. Babies may become free of certain food intolerances as they grow.

Most food allergies are lifelong conditions. Many children outgrow allergies to milk, egg, soy, and wheat, and some children outgrow nut allergies. Allergy treatments involve the careful introduction of the allergen in microscopic quantities to teach the immune system to tolerate it, but it may not work for everyone, and it is not an option for people who have severe reactions. This should only be done under the guidance of a doctor.

People with severe food allergies have a risk for anaphylaxis and may be advised by the doctor to always carry epinephrine shots (EpiPen) to be administered in an emergency.