Most food allergies start in childhood, but they can develop at any time of life. It is not clear why, but some adults develop an allergy to a food they typically eat with no problem. Sometimes a child outgrows a food allergy, but that's less likely to happen with adults.

The most common foods that cause food allergy in adults are peanuts, fish, shellfish (shrimp or lobster) and tree nuts (almonds, walnuts, pecans and cashews).

If you have a food allergy, you'll need to avoid the offending food. An allergic reaction can quickly put your immune system into a state of emergency, affecting numerous organs in your body. For certain people, even a tiny amount of the food may cause signs and symptoms such as digestive problems, hives, facial swelling or trouble breathing.

Some people with a food allergy are at risk of a life-threatening reaction (anaphylaxis) that requires emergency treatment.

Don't ignore a reaction that occurs shortly after eating a particular food. See your doctor to determine the cause of your symptoms. Even if you've had a relatively mild reaction in the past, subsequent allergic reactions may be more serious. Get emergency treatment for any severe food reaction.