Symptoms:

Symptoms usually begin immediately, seldom more than 2 hours after eating. Rarely, the symptoms may begin hours after eating the offending food.

If you develop symptoms shortly after eating a specific food, you may have a food allergy. Key symptoms include hives, hoarse voice, and wheezing. In severe reactions, you may have low blood pressure and blocked airways.

Other symptoms that may occur include:

• Abdominal pain
• Angioedema (swelling, especially of the eyelids, face, lips, and tongue)
• Diarrhea
• Difficulty swallowing
• Itching of the mouth, throat, eyes, skin, or any area
• Light-headedness or fainting
• Nasal congestion
• Nausea
• Runny nose
• Shortness of breath
• Stomach cramps
• Vomiting

Symptoms of oral allergy syndrome:

• Itchy lips, tongue, and throat
• Swollen lips (sometimes)

Signs and tests:

A blood or skin test can be done to identify elevated antibody levels (particularly IgE) and confirm that you have an allergy.

Elimination diets involve avoiding the suspected food until the symptoms disappear, then reintroduced to see if allergic reaction develops

Provocation (challenge) testing involves exposing a person to a suspected allergen under controlled circumstances. This may be done in the diet or by breathing in the suspected allergen. This type of test may provoke severe allergic reactions. Challenge testing should only be done by a doctor.

Never try to deliberately cause a reaction or reintroduce a food on your own. These tests should only be performed under the guidance of a health care provider -- especially if your initial reaction was severe.

See: Allergy testing