Food Intolerances

Intolerance, allergy and celiac disease

• Food intolerance: symptoms such as bloating, gas, diarrhea or headache, often related to the amount eaten. Examples include lactose intolerance and sensitivity to fermentable carbohydrates (FODMAPs).
• Food allergy: an immune reaction that can cause hives, swelling, breathing problems or anaphylaxis, even from small amounts. Allergies need assessment by a healthcare provider.
• Celiac disease: an autoimmune reaction to gluten that damages the small intestine.

Common symptoms and challenges

• Bloating, gas, cramping and changes in bowel habits
• Headaches, flushing or feeling unwell after certain foods or drinks
• Difficulty identifying which food is responsible, since reactions can be delayed or dose-dependent

Genetic and biological factors

Well established: Lactose intolerance in adults is largely determined by genes that control whether the lactase enzyme keeps working after childhood. Genetic differences also affect how quickly people process caffeine and alcohol. Celiac disease almost always occurs in people who carry HLA-DQ2 or HLA-DQ8.

Debated: Histamine intolerance, non-celiac gluten or wheat sensitivity, and other intolerances are recognized by many clinicians but lack reliable laboratory tests.

Laboratory testing

Clinicians often use a food and symptom diary, a supervised elimination and reintroduction, breath tests for lactose or fructose malabsorption, and blood tests for celiac disease.