What it is: While you can be allergic to gluten, celiac disease is not a food allergy. "It's a hereditary autoimmune disease that damages the small intestine and interferes with the absorption of nutrients from food," notes Scott Sicherer, M.D., a professor of pediatrics and a researcher at the Jaffe Food Allergy Institute at the Icahn School of Medicine at Mount Sinai in New York City. Left untreated, it can increase the risk of lymphoma and other types of cancer.
Symptoms: Abdominal cramping and bloating; anemia; constipation; diarrhea; fatigue; joint pain; mouth ulcers; weight loss.
How it's identified: Blood tests for gluten autoantibodies, followed by an endoscopy with a biopsy to look for damage to the small intestine.Non-Celiac Gluten Sensitivity
What it is: A condition in which you cannot tolerate gluten and have symptoms similar to those of celiac disease, but don't have the autoantibodies or damage to the small intestine that characterize the disease.
Symptoms: Bloating; diarrhea; fatigue; headache; brain fog; joint pain; numbness in the legs, arms or fingers.
How it's identified: A blood test comes up negative for celiac disease, but following a gluten-free diet leads to improved health.Food Allergy vs. Food Intolerance
What it is: The immune system produces large amounts of antibodies called immunoglobulin E (IgE) in response to a protein in a particular food, triggering allergy cells to produce chemicals (such as histamine) that cause allergic symptoms.
Symptoms: Hives, itching and/or eczema; nausea, vomiting and/or diarrhea; respiratory and cardiovascular symptoms.
Severity: It can be life-threatening even when a small amount of the offending food is eaten.
What it is: A reaction in the digestive (not the immune) system when your body is unable to properly break down certain sugars in a particular food (such as lactose in milk) due to enzyme deficiencies or sensitivity to a naturally occurring chemical in that food.
Symptoms: Bloating; gas; diarrhea; other forms of gastrointestinal discomfort.
Severity: "A food intolerance is unpleasant but not life-threatening," says Dr. Sicherer, author of Food Allergies: A Complete Guide for Eating When Your Life Depends on It. "It affects adults more than kids."