When a person has a food allergy, the body’s immune system mistakenly treats certain substances in that food—called allergens—as harmful. An allergic reaction happens when the immune system tries to fight off the allergen.

The first time a person eats a food he or she is allergic to, there is no allergic reaction. But, the immune system reacts to the food as if it was harmful and makes antibodies to fight that allergen. The next time the person eats that food, an allergic reaction occurs. It may happen within a few minutes to several hours after exposure to the allergen. Sometimes a person does not eat the allergenic food, but is exposed to it by touching it, using a skin or hair care product containing it, or being close to someone eating it.

During an allergic reaction to a food, the following symptoms may occur:

• Itching in the mouth
• Swelling of lips and tongue
• Vomiting, diarrhea, or abdominal cramps and pain
• Hives
• Worsening of eczema
• Tightening of the throat or trouble breathing
• Drop in blood pressure

The most severe allergic reaction is called anaphylaxis. This is a potentially life-threatening reaction that requires immediate medical attention because it can lead to death if breathing and blood circulation become severely restricted. Anaphylaxis has many symptoms that are similar to less serious allergic reactions, but a combination of the most severe symptoms can indicate it.

Symptoms of anaphylaxis include:

• Skin symptoms listed above or swollen lips
• Difficulty breathing
• A drop in blood pressure
• Vomiting, diarrhea or cramping

Food allergies are more common in young children than in adults. In the United States, almost 1 in 20 children under age 5—and almost 1 in 25 adults—are allergic to at least one food. People tend to outgrow some food allergies, such as milk, egg and soy. Others, like peanut allergy, can last for life.

Some people can develop a food allergy later in life. For example, milk allergy tends to develop in children, whereas shrimp allergy generally develops in adulthood. Studies show that food allergies are becoming more common, especially peanut allergy.

As your or your child’s food allergy is diagnosed, treated and managed, you may deal with several different doctors and specialists. Your care team may include some of these providers.

Allergist/immunologist: Commonly referred to as an allergist, this type of doctor is specially trained to diagnose, treat and manage food allergies, indoor or seasonal allergies, asthma, and other disorders affecting the immune system.

Pediatric allergist/immunologist: This type of doctor is specially trained to diagnose, treat and manage food allergies, indoor or seasonal allergies, asthma, and other immune disorders in children.

Internist or family physician: Doctors who provide general medical care for adults. Adults with food allergies may initially be diagnosed and treated by an internist or family physician.

Pediatrician: This type of doctor specializes in the medical care of children. Children with food allergies may initially be diagnosed and treated by a pediatrician.

You’ll probably have questions for your doctor about food allergies. Review this list of common concerns before your appointment, or print it out to bring with you.

Questions About My Diagnosis

• What makes people allergic to certain foods?
• How do I find out if there are other foods I am allergic to?
• Will I need to see a specialist for my food allergies? Will insurance pay for this?
• How often will I need to see the specialist?
• Is my food allergy life-threatening?

Questions About My Treatment

• Are there allergy shots for food allergies?
• Are there any medications to prevent or lessen the allergic reaction?
• Can I touch foods that I am allergic to?
• Will the allergic reaction be worse the next time I’m exposed to my allergenic food?

Questions About My Lifestyle and Family

• Will I have this food allergy for the rest of my life?
• Will the allergy get better or worse over time?
• Will my children inherit my food allergy?
• Are there other foods I can eat as a substitute for the ones I’m allergic to?
• Is it safe for others in my home or workplace to eat the allergenic food when I’m around?

Diagnosis of food allergy begins with the doctor asking questions about the following:

• The symptoms of your allergic reaction
• What food or foods triggered the reaction
• How fast the symptoms came on after eating the allergenic food
• How much of it you ate
• Whether other people got sick after eating that food
• Whether medications, such as antihistamines, helped relieve the symptoms
• Your overall medical history

The doctor will be trying to determine whether you or your child has an allergy to specific foods or if the symptoms are caused by food intolerance or another medical condition. If the doctor suspects a food allergy, he or she will then suggest one or more of the following:

Diet diary

• To identify a pattern of which food or foods cause symptoms
• You keep a diary in which you write down everything you eat and whether you have symptoms of an allergic reaction.

Limited elimination diet

• To see if the allergic reaction stops occurring after you remove the allergenic food or foods identified in the diet diary
• You stop eating the food that is suspected of causing an allergic reaction for a week or more.
• If you no longer have the allergic reaction after you eliminate the suspected allergenic food from your diet, this suggests that you have a food allergy.

Skin prick test

• To confirm the diagnosis of food allergy when the history, diet diary, and elimination diet suggest a food allergy
• A needle is used to place a tiny amount of food extractjust below the surface of the skin on your lower arm or back. Typically several food extracts are tested at once.
• There will be swelling or redness at the test site if you are allergic to that food. It’s possible to test positive even if you are not allergic to that food. Diagnosis is made based on having both a history of allergic reactions to that food and a positive skin prick test.

Blood test

• To measure the levels of food-specific antibodies in the blood
• The presence of antibodies to a food suspected of being an allergen indicates a food allergy. It’s possible to test positive even if you are not allergic to that food. Diagnosis is made based on having both a history of allergic reactions to that food and a positive blood test.

Oral food challenge

• The final method used to diagnose food allergy
• A healthcare professional gives you single doses of various foods, some of which are the foods suspected of starting an allergic reaction. He or she watches to see if an allergic reaction occurs after each food.
• If you have an allergic reaction only to certain foods and not to others, allergy to the allergenic foods is confirmed.

Treatment for food allergy involves avoiding the foods that cause your allergic reaction. This means removing those foods from your or your child’s diet and, for some people, removing them from your home and workplace.

Reading Food Labels

In order to avoid foods that are used as ingredients in packaged foods, you will need to check food labels to see if the food contains any of the allergens. The U.S. Food and Drug Administration requires that food labels have a section for listing potentially allergenic foods, such as nuts, milk, eggs and soy.

Cleaning

Some people with a food allergy have an allergic reaction just from touching the allergenic food. If you or your child has this type of food allergy, it’s important that family and friends wash their hands with soap and water and clean counters and tables after eating or handling the allergenic food.

EpiPen

An EpiPen is an auto-injection device that contains the medication epinephrine (also called adrenaline). Epinephrine stops or limits the allergic reaction until you can get medical attention. People with food allergies need to carry an EpiPen in case they accidentally eat one of their allergenic foods.