What’s the difference between being allergic to a food and being sensitive or intolerant to it?

The difference between a food allergy and sensitivity is the body’s response. When you have a food allergy, your immune system causes the reaction. If you have a food sensitivity or intolerance, the reaction is triggered by the digestive system.

  • Symptoms of food intolerance include gas, bloating, diarrhea, constipation, cramping, and nausea.
  • Symptoms of food allergy include hives, swelling, itching, anaphylaxis, and dizziness.

Food sensitivities

Sherry Farzan, MD, allergist and immunologist with North Shore-LIJ Health System in Great Neck, N.Y., says that that food sensitivities are not life-threatening. She explains that there are food intolerances that are not immune-mediated. Instead they’re caused by an inability to process or digest a food.

Food sensitivities and intolerances are more common than food allergies, according to the British Allergy Foundation. Neither involves the immune system.

A food triggers an intolerance in your digestive tract. This is where your body can’t properly break it down, or your body reacts to a food you’re sensitive to. For example, lactose intolerance is when your body can’t break down lactose, a sugar found in dairy products.

You may be sensitive or intolerant to a food for a few reasons. These include:

  • not having the right enzymes you need to digest a certain food
  • reactions to food additives or preservatives like sulfites, MSG, or artificial colors
  • pharmacological factors, like sensitivity to caffeine or other chemicals
  • sensitivity to the sugars naturally found in certain foods like onions, broccoli, or Brussels sprouts

Symptoms of food sensitivity vary. But the symptoms of intolerance are all digestive-related. These can include:

  • gas and bloating
  • diarrhea
  • constipation
  • cramping
  • nausea

Food allergies

Your immune system is your body’s defense against invaders like bacteria, fungus, or the common cold virus. You have a food allergy when your immune system identifies a protein in what you eat as an invader, and reacts by producing antibodies to fight it.

Farzan explains that a food allergy is an immune-mediated reaction to the food. The most common is an immunoglobulin E (IgE)-mediated reaction. IgEs are allergic antibodies. They cause an immediate reaction when chemicals, like histamine from mast cells, are released.

Food allergies can be fatal, unlike a food intolerance or sensitivity. In extreme cases, ingesting or even touching a small amount of the allergen can cause a severe reaction.

Symptoms of food allergy include:

  • skin reactions, like hives, swelling, and itching
  • anaphylaxis, including difficulty breathing, wheezing, dizziness, and death
  • digestive symptoms

Eight foods account for 90 percent of allergic reactions: milk, eggs, fish, shellfish, peanuts, tree nuts, wheat, and soybeans.

There are also non-IGE mediated food allergies. These reactions occur when other parts of the immune system are activated apart from IGE antibodies.

The symptoms of non-IGE reactions are typically delayed, and occur primarily in the gastrointestinal tract. They include vomiting, diarrhea, or bloating. Less is known about this particular type of reaction, and in general this type of response is not life-threatening.

What to do in an emergency

Eight foods account for 90 percent of allergic food reactions. These are:

  • milk
  • eggs
  • fish
  • shellfish
  • peanuts
  • tree nuts
  • wheat
  • soybeans

People who have food allergies must avoid these foods. Also, the parents and caretakers of a child with food allergies must be trained to treat accidental ingestions, says Farzan.

Self-injectable epinephrine must always be available, and parents and caretakers should know how to administer the injectable, she explains.

The potential effects of an allergic reaction are severe. But efforts are made to accommodate people with food allergies. School lunchrooms may be peanut-free to cater to children with peanut allergies.

Also, it’s required that product labels state if a food is made in the same facility that processes the most common allergens.