What are the symptoms of a food allergy?

Food allergies—like other types of allergies—are caused by faulty triggers in the immune system. They usually happen when the body's immune system mistakenly thinks something in a food—usually a protein—is a potential invader. In defense, the immune system releases chemicals that cause unpleasant, and sometimes, life-threatening symptoms.

Allergic reactions occur very quickly—typically within a few minutes to one hour after ingesting an offending food. Symptoms vary and may include:

• itching or tingling in the mouth, lips, or throat
• trouble swallowing or a tight feeling in the throat
• asthma-like symptoms, such as trouble breathing, coughing, or wheezing
• runny nose
• stomach pain, diarrhea, vomiting, or nausea
• hives or a skin rash
• swelling of the face or other parts of the body.

In babies, food allergies can cause diarrhea, bloody stools, and trouble sleeping.

Some people with food allergies experience a severe reaction known as anaphylaxis. When this potentially deadly reaction occurs, the symptoms mentioned above become severe. In some cases, blood pressure may drop, and the person may faint. Anaphylaxis requires immediate, emergency treatment.