What is food allergy?

A food allergy is an abnormal response of the body's immune system to certain foods. This is not the same as food intolerance, although some of the symptoms may be very similar.

What causes food allergies?

Your body’s immune system fights off infections and other dangers to keep you healthy. When your immune system senses that a food or something in a food is a “danger” to your health, you have a food allergy reaction. Your immune system sends out immunoglobulin E or IgE antibodies. These react to the food or substance in the food. This can cause allergy symptoms such as hives, asthma, itching in the mouth, trouble breathing, stomach pains, vomiting, or diarrhea.

Which foods most often cause food allergies?

About 9 in 10 food allergies are caused by these foods:

• Milk

• Eggs

• Wheat

• Soy

• Tree nuts

• Fish

• Shellfish

• Peanuts

Some facts about food allergies:

• Eggs, milk, and peanuts are the most common causes of food allergies in children.

• Peanuts, tree nuts, fish, and shellfish commonly cause the most severe reactions.

• Nearly 1 in 20 children under the age of 5 years have food allergies.

• From 1997 to 2007, food allergies increased by 18% among children under age 18 years.

• Most children "outgrow" their allergies. But allergies to peanuts, tree nuts, and shellfish may be lifelong.

• According to the National Institute of Allergy and Infectious Diseases, it doesn't take much food to cause a severe allergic reaction—1/44,000 of a peanut can cause a severe reaction in a highly allergic person.

What are the symptoms of food allergies?

Allergic symptoms may begin within minutes to an hour after eating the food. The following are the most common symptoms of a food allergy. But symptoms may occur a bit differently for each person. Symptoms may include:

• Swelling and itching of lips and mouth

• Tightness in the throat or hoarse voice

• Nausea and vomiting

• Diarrhea and cramps

• Itchy, raised bumps (hives)

• Swelling of the skin

• Itching

The symptoms of a food allergy may look like other health conditions or problems. Always talk with your healthcare provider for a diagnosis.

What are severe symptoms of food allergy?

Anaphylaxis is a severe allergic reaction. It is life-threatening. Symptoms can include those above as well as the following:

• Trouble breathing or wheezing

• Feeling as if the throat is closing or that the lips and tongue are swelling 

• Flushing of the skin

• Itching of palms and soles of feet

• Feeling faint

• Nausea

• Fast pulse

• Low blood pressure

• Loss of consciousness

Anaphylaxis is a medical emergency. Call 911 to get help right away. Severe allergic reactions are treated with epinephrine. If you know you have severe allergies, you should carry an emergency kit with self-injecting epinephrine or Epi-pens.

Treatment for food allergies in adults

The goal of treatment is to stay away from the food that causes the allergic symptoms. There is no medicine to prevent food allergies, although research is ongoing.

You need to be prepared in case you eat something with the food that causes your allergic reaction. You may need an emergency kit to stop severe reactions. Talk with your healthcare provider about what you should do.

Medicines are available for some symptoms caused by food allergy after the food has been eaten. Discuss available medicines with your healthcare provider.

Treatment of food allergies in children

As in adults, it is very important that your child stays away from foods that cause allergies. If you are breastfeeding your child, it is important that you not eat foods to which your child is allergic.

You may need to give vitamins to your child if he or she is unable to eat certain foods. Discuss this with your child's healthcare provider.

Your child's healthcare provider may also prescribe an emergency kit.  Be sure to ask your child's healthcare provider about an emergency kit if you don't already have one.

Some children under the supervision of their healthcare provider may be given certain foods after a period of 3 to 6 months. This finds out if the child has outgrown the allergy.