Because they can cause somewhat similar symptoms, food allergy and food intolerance can easily be confused. Most abnormal reactions to food, however, are related to food intolerance rather than food allergy. Typically, signs of food intolerance show up more gradually and are milder than those of food allergy, which involve the immune system and can cause deadly reactions. Here, tips from Rauno Joks, MD, chief of the Division of Allergy & Immunology at the SUNY Downstate Medical Center on deciphering between the two.

Food Allergy

“Food allergy is a specific immune response to a food,” says Dr. Joks, “which means the immune system perceives a component of the the food as a threat and overreacts to its ingestion. This reaction can be life-threatening.” Food allergy symptoms tend to include nausea, vomiting, stomach pain, and diarrhea.

Common Food Allergies:

  • Fish and shellfish (including crab, lobster, shrimp)
  • Peanuts
  • Tree nuts (including almonds, cashews, pecans, walnuts)
  • Eggs

Food Intolerance

By comparison, a  food intolerance is an inability to digest a food, which can cause GI irritability (including indigestion). Food intolerance symptoms are usually limited to the digestive system and tend to be milder than food-allergy symptoms. With a food intolerance, according to the Mayo Clinic, you can sometimes still have a small amount of the problem food; whereas with a food allergy, you are advised to not have any of the offending food ever–to give it up entirely–because any amount could cause an immediate, serious reaction.

Common Food Intolerances:

  • Gluten: An inability to tolerate gluten, which is part of barley, rye, and wheat.
  • Lactose: When the body lacks the lactase enzyme in the gut and can’t digest lactose (a sugar in milk).
  • Food additives: When the body reacts to items added to food (including MSG or sulfites) that change color or taste or to prevent bacteria. Symptoms include headache, flushing, heat, and chest discomfort.

Similarities

Both occur as reactions to food.

Differences

While certainly food intolerance can cause a lot of discomfort, in general, food intolerance is not dangerous, says Dr. Joks. The one exception may be a sensitivity to sulfites, which can trigger acute asthma.

If you believe you’ve had a negative reaction to a certain food, it is best to work with an allergist who can do the detective work needed, which may include blood and skin tests, to determine which condition you may have, says Dr. Joks. If you do not have an allergist, make an appointment with your physician who can refer you to a specialist.

Are there foods You are allergic to or intolerant of?