Food Allergy

What is a food allergy?

A food allergy is a reaction by the body's 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). Food allergies must be taken seriously. Very tiny amounts of a food can cause a reaction if you are allergic to it, and a severe reaction can be sudden and life threatening.

How does it occur?

A food allergy occurs when the body's immune system mistakenly believes that a harmless substance (a food) is harmful. In order to protect the body, the immune system creates substances called antibodies to that food. The next time you eat that particular food, your immune system releases huge amounts of chemicals, such as histamines, to protect the body. These chemicals trigger symptoms that can affect the respiratory and cardiovascular systems, gastrointestinal tract, and skin.

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
• seafood, especially shellfish
• wheat
• soy.

People who have asthma have an increased risk of a severe or fatal reaction.

What are the symptoms?

Reactions differ. They may occur right away or not for several hours. Symptoms may be mild, or they might be life threatening when the allergy causes breathing problems.

Symptoms may include:

• skin rash or hives
• itching
• swelling in the lips, face, throat, or other part of the body
• nausea or vomiting
• diarrhea
• stomach cramps
• wheezing or trouble breathing
• coughing
• trouble swallowing
• throat tightness or closing
• red, watery eyes
• fainting
• dizziness
• change of voice.

The symptoms of a severe reaction generally occur within minutes to 2 hours after contact with the food causing the reaction. In rare instances symptoms may occur up to 4 hours later.

Some fresh fruits and vegetables can cause a mild allergic reaction called oral allergy syndrome. The itching or tingling of the mouth that occurs is not a true allergy. Instead, it is the result of cross-reactivity: These foods contain some of the same proteins that are found in certain pollens that you may be allergic to. For example, if you are allergic to ragweed, you may react to eating melons and bananas. An allergy to birch pollen may cause a reaction to apples, plums, and nectarines.

How is it diagnosed?

Your healthcare provider will ask about your symptoms and the foods you eat. 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 a while. Then you can carefully try eating these foods again, one by one, to see if your symptoms come back. Ask your provider which foods you should avoid at first.

Your healthcare provider may recommend that you keep a food diary. This involves recording all of the food you eat and when you eat it. You should also record any symptoms you may have.

If your symptoms are severe and there is no obvious cause, then it may be possible to have allergy skin tests or blood tests for common food allergies such as egg, cow's milk, nuts, and shellfish.

How is it treated?

There is no cure for food allergy. Strict avoidance of foods you are allergic to is the only way to prevent a reaction.

If you have sudden, severe food allergy symptoms or your symptoms do not get better and you start having throat tightness or trouble breathing, call 911 for emergency help.

For severe reactions, you may need a shot of epinephrine.

Mild symptoms may not need treatment. Or your healthcare provider may prescribe antihistamines for you to use as needed. For moderate symptoms your provider may also prescribe a steroid medicine for you to use for a short time.

If you have had one or more severe reactions to food, ask your provider if you should carry injectable epinephrine (EpiPen) with you. A shot with the EpiPen given by yourself or a friend can slow down a severe reaction while you wait for medical help to arrive.

How long will the effects last?

The effects of the allergic reaction last from several minutes to hours, depending on how much of the food you ate and the severity of your allergy.

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

How can I take care of myself and help prevent an allergic reaction to food?

• The only way to not have a reaction is to avoid the food that causes the allergy symptoms. When you know you are allergic to a specific food, you should avoid eating that food. Be sure to check the ingredients on food package labels and ask about the ingredients in foods prepared in restaurants when you eat out.
• Follow all of your healthcare provider's instructions.
• Keep track of all reactions for yourself and your healthcare provider.
• Substitute soy-based products for milk if you are allergic to milk but not to soy. If you are allergic to both milk and soy, substitute rice or nut-based milk. Look for rice or nut milks that are calcium enriched.
• If you tend to have severe food allergy reactions, you should ask your healthcare provider about carrying medicine with you, such as injectable epinephrine (EpiPen), for emergency use. Tell others about your allergy; that is, what you need to avoid, the symptoms of an allergic reaction, and how they can help during an allergic emergency.
• Wear a medical ID bracelet or necklace that notes your allergy. Or you can carry a card in your wallet or purse.
• For more information, contact:

  The Food Allergy & Anaphylaxis Network (FAAN)
  Phone: (800) 929-4040
  Web site: http://www.foodallergy.org.

  The American Academy of Allergy, Asthma and Immunology
  Web site: http://www.aaaai.org