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Food allergy

Definition

A food allergy is type of immune response triggered by eggs, peanuts, milk, or some other specific food.

Test Your Food Allergies IQ

What are common symptoms of food allergies?

The correct answer is all of the above. Eating something you're allergic to can trigger symptoms ranging from a runny nose to a dangerous full-body reaction. Talk to your doctor if you have any of these symptoms after eating a food, even if it's a small reaction.

Food allergy and food intolerance are the same.

The correct answer is false. A food allergy occurs when your immune system overreacts to a food and releases the chemical histamine. This causes allergic symptoms. Food intolerance is more common and doesn't involve your immune system. Sometimes it occurs because you can't digest part of a food, such as lactose, a type of sugar in milk.

Which is a common food allergy?

The correct answer is all of the above. Any food can cause an allergic reaction, but these are the most common. Other common foods include shellfish, soy, and tree nuts.

If you eat something you're allergic to, your body will react within:

The correct answer is two hours. Rarely, the symptoms may begin several hours after eating the food. Mild symptoms, such as a hive on your chin after eating something, will disappear soon and do not require treatment. However, you should tell your doctor about it.

For some people, food allergies can be life-threatening.

The correct answer is true. Some people have a severe allergic reaction, called anaphylaxis. This causes a whole-body reaction. Symptoms can start within minutes and may include breathing and swallowing problems, slurred speech, or passing out. If you have any of these symptoms, call 9-1-1 right away.

The only proven treatment for a food allergy is to avoid the food.

The correct answer is true. If you're allergic to a food, the best way to prevent a reaction is to cut the food from your diet. Other treatments, such as allergy shots and probiotics, don't work to treat food allergies.

Many children outgrow their allergy to:

The correct answer is eggs. Many children will outgrow their allergy to eggs, milk, wheat, and soy by the time they are 5 years old if they avoid that food when they are young. Allergies to peanuts, tree nuts, and shellfish tend to last a lifetime.

To find out if you're still allergic to a food, you should eat a small amount.

The correct answer is false. Do not eat a food that caused a reaction in the past without checking with your doctor first. A mild reaction in the past can become a more severe reaction the second or third time you try a food. Your doctor may want to be present when you try the food.

People with food allergies should always carry epinephrine.

The correct answer is true. Epinephrine is a medicine you can carry with you. It can stop a severe allergic reaction and save your life. It comes in a small syringe that is ready for you to give yourself a shot. If you've had an allergic reaction to food -- even a mild reaction -- talk to your doctor about this medicine.

If you begin wheezing after eating a food, you should:

The correct answer is to inject epinephrine and then call 9-1-1. Make sure you know how to use it. Also show loved ones how to use it in case you can't inject yourself.

Fresh fruits are a common cause of mouth allergies.

The correct answer is true. If you have an allergy to fruit, melons, apples, pineapple, and other fruits can cause your lips, tongue and throat to itch – especially if you eat them raw. The more fruit you eat, the more severe the reaction. A more severe reaction is rare.

Which of the following may prevent food allergies in children?

The correct answer is breastfeeding. Waiting to add allergy-causing foods until your baby is a little older also may help. The timing for this varies from food to food and from baby to baby. Ask your child’s health care provider when is best to start certain foods that commonly cause allergic reactions.

Alternative Names

Allergy to food

Causes

Many people have a food intolerance. This term refers to heartburn, cramps, belly pain, or diarrhea that can occur after they eat foods such as:

A true food allergy is much less common.

The immune system normally protects the body against harmful substances, such as bacteria and viruses. It also reacts to foreign substances called allergens. These are usually harmless and in most people do not cause a problem.

Food allergies

Food allergies

In a person with a food allergy, the immune response is oversensitive. When it recognizes an allergen, the immune system launches a response. Chemicals such as histamines are released. These chemicals cause allergy symptoms.

Any food can cause an allergic reaction. The most common food allergies are to:

  • Eggs (mostly in children)
  • Fish (older children and adults)
  • Milk (people of all ages)
  • Peanuts (people of all ages)
  • Shellfish such as shrimp, crab, and lobster (people of all ages)
  • Soy (mostly in children)
  • Tree nuts (people of all ages)
  • Wheat (people of all ages)

In rare cases, food additives, such as dyes, thickeners, and preservatives, can cause a food allergy or intolerance reaction.

Some people have an oral allergy. This is an allergy type syndrome that affects the mouth and tongue after they eat certain fresh fruits and vegetables:

  • Melons, apples, pineapple, and other foods contain substances that are similar to certain pollens.
  • The reaction most often occurs when you eat the raw form of the foods. How severe the reaction is depends on how much of the food you eat.

Symptoms

Symptoms usually begin within 2 hours after eating. Sometimes, the symptoms begin hours after eating the food.

Key symptoms of a food allergy include hives, a hoarse voice, and wheezing.

Other symptoms that may occur include:

Dermatitis, perioral

Dermatitis, perioral

Symptoms of mouth (oral) allergy syndrome:

  • Itchy lips, tongue, and throat
  • Swollen lips (sometimes)

In severe reactions, you may have low blood pressure and blocked airways.

Exams and Tests

Blood or skin tests are sometimes used to confirm that you have an allergy. A double-blind food challenge is one way to diagnose true food allergies. During this test, you and your health care provider will not know what you are eating.

With elimination diets, you avoid the suspected food until your symptoms disappear. Then you start eating the foods again to see if you develop an allergic reaction.

In provocation (challenge) testing, you eat a small amount of the suspected food under medical supervision. This type of test may cause severe allergic reactions. Challenge testing should only be done by a health care provider.

Never try to cause a reaction or reintroduce a food on your own. These tests should only be done under the guidance of a health care provider, especially if your first reaction was severe.

Treatment

If you suspect that you or your child has a food allergy, see an allergy specialist doctor (allergist).

Treatment may involve any of the following:

  • Avoiding the food (this is the most effective treatment)
  • Desensitization, during which you eat a small amount of the food each day. This must be done under an allergist's guidance.

Other treatments, including allergy shots and probiotics, have not been proven to help with food allergies.

If your child has a problem with cow's milk formula, your provider may suggest trying a soy-based formula or something called an elemental formula, if it is available.

If you have symptoms on only one area of the body, for example, a hive on the chin after eating the food, you may not need any treatment. The symptoms will likely go away in a brief time. Antihistamines may relieve the discomfort. Soothing skin creams may also provide some relief.

If you have been diagnosed with a food allergy, learn how to use injectable epinephrine. You should have it with you at all times. If you develop any type of serious or whole-body reaction (even hives) after eating the food:

  • Inject the epinephrine.
  • Then go to the nearest hospital or emergency facility right away, preferably by ambulance.

Support Groups

Food Allergy and Research and Education (FARE) -- www.foodallergy.org

Outlook (Prognosis)

Many children outgrow their allergy to milk, egg, wheat, and soy by 5 years old if they avoid that food when they are young. Allergies to peanuts, tree nuts, and shellfish tend to last a lifetime.

Read food labels

Read food labels

Avoiding the problem foods may be easy if the food is uncommon or easy to identify. When eating away from home, ask detailed questions about the food you are served. When buying food, read package ingredients carefully.

Possible Complications

Anaphylaxis is a severe, whole-body allergic reaction that is life threatening. Although people with oral allergy syndrome may have an anaphylactic reaction in rare cases, they should ask their doctor if they need to carry injectable epinephrine.

Food allergies can trigger or worsen asthma, eczema, or other disorders.

When to Contact a Medical Professional

  • Call your local emergency number, such as 911, if you have any serious or whole-body reactions, particularly wheezing or difficulty breathing, after eating a food.
  • If your doctor prescribed epinephrine for severe reactions, inject it as soon as possible, even before calling 911. The sooner you inject the epinephrine, the better.
  • Anyone who has had an allergic reaction to a food should be seen by an allergist.

Prevention

Breastfeeding may help prevent allergies. Otherwise, there is no known way to prevent food allergies except to delay introducing allergy-causing foods to infants until their gastrointestinal tract has had a chance to mature. The timing for this varies from food to food and from baby to baby.

Once an allergy has developed, carefully avoiding the offending food usually prevents further problems.

Images

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Anaphylaxis
Food allergies
Read food labels
Dermatitis, perioral
Antibodies

References

Bohl B. Food allergy. In: Rich RR, Fleisher TA, Shearer WT, et al, eds. Clinical Immunology. 4th ed. Philadelphia, PA: Elsevier; 2013:chap 43.

NIAID-sponsored expert panel, Boyce JA, Assa'ad A, et al. Guidelines for the Diagnosis and Management of Food Allergy in the United States: Report of the NIAID-Sponsored Expert Panel. J Allergy Clin Immunol. 2010;126 (6 Suppl):S1-S58. PMID: 21134576 www.ncbi.nlm.nih.gov/pubmed/21134576.

Sicherer SH, Lack G, Jones SM. Food allergy management. In: Adkinson NF Jr., Bochner BS, Burks AW, et al, eds. In: Middleton's Allergy Principles and Practice. 8th ed. Philadelphia, PA: Elsevier Mosby; 2013:chap 84.

Review Date: 
11/4/2014
Reviewed By: 
Stuart I. Henochowicz, MD, FACP, Associate Clinical Professor of Medicine, Division of Allergy, Immunology, and Rheumatology, Georgetown University Medical School, Washington, DC. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.

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