Affecting over 2 million Americans and increasing in both incidence and severity, food allergies occur when a person’s immune system is triggered by a type of food or ingredient and “overreacts” to it, flooding the body with antibodies and hormones that cause itching, swelling, and other symptoms. The substance that sets off the reaction is called an allergen, and examples include milk, shellfish or peanuts.

In addition to hives, itching and gastrointestinal symptoms, the person experiencing a food allergy reaction may develop anaphylaxis, a life-threatening medical emergency characterized by rapid heartbeat, swelling of the lips, tongue and throat, confusion and difficulty breathing.

Most true food allergies develop in childhood, and are different from food intolerance, which is a separate condition that does not involve an immune system reaction.

For people with food allergies (or parents of affected children), a doctor may be able to identify a food allergy through a combination of history and physical exam, skin test, blood test, or carefully-supervised food challenge. Once the allergen is identified, it’s essential to avoid that food. Adults and children with severe food allergies may carry an emergency injection kit of epinephrine in case of accidental consumption.