DEAR DOCTOR K: What is the difference between a food allergy and a food intolerance?

DEAR READER: They both involve food, but other than that, food allergies and food intolerances have little in common.

Food allergies are orchestrated by the body’s immune system. Food intolerance results from the gut’s inability to digest food normally. Food allergies can be fatal; food intolerance causes discomfort but is not usually serious.

Food allergies require eliminating all traces of the food from your diet. Food intolerances can be managed without such drastic measures.

A food allergy is the immune system’s overreaction to a normally harmless food. The most common foods that people are allergic to are milk, eggs, peanuts, tree nuts, fish, shellfish, wheat and soy.

When someone with a food allergy eats an offending food, the immune system springs into action. Immune cells release chemicals that stimulate nerves, dilate blood vessels and cause inflammation. This can cause lightheadedness; itching, hives or rash; swelling of the lips, tongue and throat; and nausea, vomiting, cramping and diarrhea.

Food intolerance results from the body’s inability to properly digest or metabolize a food. Symptoms include gas, bloating, nausea and diarrhea. Lactose, a milk sugar, and gluten, a protein in grains, are the substances that people are most likely to be intolerant or sensitive to. Intolerance to lactose leads to cramping pain in the abdomen and loose bowel movements.

The reaction to gluten can range from mild to severe. With severe intolerance, the intestines produce so much uncontrollable diarrhea that a person can suffer from severe dehydration – severe enough that if the fluid is not promptly replaced, they can die.

One common and effective way to reduce symptoms is enzyme supplementation. Say you’re lactose intolerant. Taking a supplement that contains lactase can help you digest the lactose in dairy foods.

There is no similar antidote to gluten. A person with gluten intolerance needs to avoid any foods that contain gluten.