What is a food allergy?

A food allergy is a reaction by your immune system to something you ate or drank. Food allergies are more common in young children and in people who have other allergies, such as hay fever and eczema (dry skin rash). Most food allergies start during childhood, but they can start at any age. You can also have a new allergy to foods that you have eaten for years without a problem. Very small amounts of a food can cause an allergic reaction. A severe reaction can be sudden and life threatening.

What is the cause?

Allergies are a reaction your body has to things it sees as harmful. Sometimes your body’s immune system treats certain foods as though they are harmful. Your immune system tries to protect you by making antibodies. These antibodies cause your cells to release chemicals such as histamines. These chemicals cause a rash, itching, swelling, irritation, and tight muscles in your airways that make it hard for you to breathe. People who have asthma have an increased risk of a severe or life-threatening reaction.

Many different foods can cause an allergic reaction. The foods that most often cause a reaction are:

• Cow’s milk
• Eggs
• Peanuts
• Tree nuts, such as walnuts and cashews
• Fish
• Shellfish
• Wheat
• Soy

Some fresh fruits and vegetables can cause itching or tingling of the mouth. This is not an allergy to these foods, but is more likely to happen if you are allergic to certain pollens. If you are allergic to ragweed, you may react to eating melons and bananas. If you are allergic to birch pollen, you may react to eating apples, plums, and nectarines.

What are the symptoms?

Symptoms may be mild, or they might be life threatening if the allergy causes breathing problems. Common symptoms of an allergy are:

• Sneezing
• Itchy, watery eyes and swollen eyelids
• Stuffy or runny nose
• Red, raised, itchy areas on the skin (hives)
• Nausea or stomach cramps

Some of the symptoms of a severe allergic reaction are:

• Trouble talking, trouble breathing, and wheezing
• Fast heartbeat
• Swelling of the lips, tongue, or throat
• Feeling very anxious or confused
• Feeling dizzy or faint
• Vomiting or diarrhea

An allergic reaction to a food usually starts within minutes but may be delayed 2 to 4 hours. It usually lasts less than 1 day. The more severe the allergy, the smaller the amount of food it takes to cause a reaction.

How is it diagnosed?

Your healthcare provider will ask about your personal and family history for allergies. You will be asked about your symptoms and the foods you eat.

To find foods that may be causing allergic symptoms, your healthcare provider may tell you to record:

• All the foods that you eat, including toppings, mayonnaise, and sauces
• How much (serving sizes) you eat of each food
• The times of day when you eat
• Any symptoms you have after eating a food
• The time symptoms started and how long they lasted

If your symptoms are not severe, your provider may suggest that you try to find which foods cause your symptoms by not eating certain foods for awhile. Then you can carefully try eating these foods again, one at a time, to see if your symptoms come back. Ask your provider which foods you should avoid at first.

Your healthcare provider may advise you to have tests to check for food allergies. This will help you know which foods you should avoid eating to prevent an allergic reaction.

How is it treated?

Mild symptoms may not need treatment. Your healthcare provider may suggest antihistamine medicine.

For moderate symptoms your provider may prescribe a steroid medicine for you to use for a short time. Using a steroid for a long time can have serious side effects. Take steroid medicine exactly as your healthcare provider prescribes. Don’t take more or less of it than prescribed and don’t take it longer than prescribed. Don’t stop taking a steroid without your provider’s approval. You may have to lower your dosage slowly before stopping it.

Severe reactions are an emergency. You need to be treated with a shot of epinephrine and other medicines. You will need to be watched in the hospital for several hours to make sure that your symptoms do not come back after the effects of the medicine have worn off. If you have been diagnosed with a severe food allergy, you may need to carry an epinephrine emergency kit with you at all times.

Treating a food allergy with drops or shots that contain small amounts of the allergen is called immunotherapy or desensitization. This may allow you to have a less severe allergic reaction to the food. This treatment must be done only by a trained healthcare provider. The process can take a few years. It is not yet known if this is a safe and effective way to treat food allergies.

Some food allergies are outgrown while others are lifelong. Most children outgrow allergies to milk, eggs, soy, and wheat. However, allergies to peanuts, nuts, fish, and shellfish are almost never outgrown.

How can I take care of myself?

• When you know that you are allergic to a certain food, you need to avoid eating that food. Be sure to check the ingredients on food package labels. Ask about the ingredients in foods and how they are prepared when you order food at restaurants and when you eat food prepared by other people, such as at a dinner party.
• Babies are not allergic to breast milk, but they can react to things that the mother eats that pass into breast milk. If a certain food or drink seems to upset your baby, avoid that food or drink for a couple of weeks before you try it again.
• Follow all of your healthcare provider’s instructions.
• Keep a record of all reactions you have to food or drink.
• Tell family, friends, and coworkers about your allergy. Let them know what you need to avoid, what symptoms you may have, and how they can help if you have a severe reaction.
• Carry an ID card or medical ID bracelet that says you have an allergy.

How can I prevent food allergies?

Breast-feed your baby. Babies who are breast-fed for 6 to 12 months tend to have fewer allergies, and are less likely to have skin problems and asthma than babies fed with formula. Slowly introducing foods after the age of 4 to 6 months may also help.

For more information, contact:

• The Food Allergy & Anaphylaxis Network (FAAN)
  800-929-4040
  http://www.foodallergy.org.
• The American Academy of Allergy, Asthma and Immunology
  http://www.aaaai.org