What causes food allergy?

A true food allergy involves your body's immune system response to a specific food or component of a food. Your immune system produces immunoglobulin E (IgE) antibodies to fight against even a tiny amount of the culprit food or food component (the allergen). This in turn releases histamine and other chemicals that cause the distressing signs and symptoms that may be a threat to life. Histamine is partly responsible for most allergic responses, including dripping nose, itchy eyes, dry throat, rashes and hives, nausea, diarrhea, labored breathing and even anaphylactic shock.

What are the risk factors for food allergy?

Several factors may put you at greater risk of developing a food allergy: • Genetic disposition. You're at increased risk of food allergies if other allergies such as hay fever, asthma, hives or eczema are common in your family. • Age. Food allergies are most common in children, especially toddlers and infants. As you grow older, your digestive system matures and your body is less likely to absorb food or food components that trigger allergies. Fortunately, children typically outgrow allergies to milk, soy, wheat and eggs. Severe allergies and allergies to nuts and shellfish are more likely to be lifelong. • Asthma.

How is food allergy diagnosed?

The following may help your doctor determine whether you have an actual food allergy: • A history of your symptoms - which foods, and how much, seem to cause problems - and whether you have a family history of food allergies. • A food diary of your eating habits, symptoms and medication use. • A physical examination to further identify or exclude other medical problems. • Skin prick tests using food extracts to determine your reaction, or a blood test that measures IgE antibody. However, these tests aren't 100-percent accurate. • Eliminating suspect foods. For a week or two, you may be asked to eliminate suspect foods and add the items back into your diet one at a time.

How is food allergy treated?

For a severe reaction to a food allergy, you may need an emergency injection of adrenaline (epinephrine) and a trip to the emergency room. If a reaction to certain foods is an annoyance, but not life-threatening, your doctor may prescribe antihistamines to block the symptom-producing release of histamine by your immune system. Creams may relieve skin reactions.

Can food allergy be prevented?

The best way to prevent an allergic reaction is to know and avoid foods that cause symptoms. Some people may be merely inconvenienced by this, but others may find it a greater hardship. For instance, if beans are a staple part of your diet, it can be a challenge to come up with a substitute that has equal nutritional value. Also some foods - when used as ingredients in certain dishes - may be well hidden. This is especially true in restaurants and in other social settings. If you know you have a food allergy, follow these steps: • Know what you're eating and drinking. Be sure to read food labels. • If you have already had a severe reaction, wear a medical alert bracelet or necklace.

Guide

Food allergy

David Cohen, M.D.Published 13 July 20047 min read

Key points

If you encounter an unpleasant reaction after eating certain foods - hives, itching, swelling or trouble breathing - you may have a food allergy.
Some of the medications used to treat respiratory allergy symptoms include antihistamines, decongestants, nasal sprays and eyedrops.
If your reaction to a certain food becomes more than an inconvenience or the symptoms are severe, talk with your doctor.
Reactions to certain foods are uncomfortable for most people, but for others they are frightening and possibly life-threatening.

Overview

If you encounter an unpleasant reaction after eating certain foods - hives, itching, swelling or trouble breathing - you may have a food allergy. Then again, you might not.

Many Americans believe they're allergic to specific foods. But true food allergies aren't as common as you might think. Less than 2 percent of adults and 8 percent of children actually have a true food allergy. This is little consolation if you've had a bad experience and fear a recurrence. That's why it's important to distinguish a food allergy from more common problems such as food intolerance, indigestion or other conditions.

Allergy Relief

Some of the medications used to treat respiratory allergy symptoms include antihistamines, decongestants, nasal sprays and eyedrops.

What do medications do?

Allegra D
Allegra
Claritin-D
Flonase
Nasacort
Nasacort AQ
Nasonex
Patanol
Zyrtec

If your reaction to a certain food becomes more than an inconvenience or the symptoms are severe, talk with your doctor. Tests can help diagnose food allergies, and you can take precautions to help prevent serious and even life-threatening responses to consuming culprit foods.

Signs and symptoms

Reactions to certain foods are uncomfortable for most people, but for others they are frightening and possibly life-threatening. Symptoms of a food allergy usually develop within an hour of eating the offending food.

The most common signs and symptoms of a true food allergy include:

Hives, itching or eczema
Swelling of the lips, face, tongue and throat, or other parts of the body
Wheezing, nasal congestion or trouble breathing
Abdominal pain, diarrhea, nausea or vomiting
Dizziness, lightheadedness or fainting

In a severe allergic reaction to food, you may have more extreme versions of the above reactions, or you may experience the following life-threatening signs and symptoms:

Constriction of airways, including a swollen throat, resulting in trouble breathing
Shock, with a severe drop in blood pressure
Rapid pulse

Written and revised by

David Cohen, M.D.

Our doctors write and review articles for accuracy and keep them up to date.

health.am provides general information, not medical advice. Always consult a qualified health professional about your own health.

Explore health topics

Food allergy

David Cohen, M.D.Published 13 July 20047 min read

Key points

If you encounter an unpleasant reaction after eating certain foods - hives, itching, swelling or trouble breathing - you may have a food allergy.
Some of the medications used to treat respiratory allergy symptoms include antihistamines, decongestants, nasal sprays and eyedrops.
If your reaction to a certain food becomes more than an inconvenience or the symptoms are severe, talk with your doctor.
Reactions to certain foods are uncomfortable for most people, but for others they are frightening and possibly life-threatening.

Overview

If you encounter an unpleasant reaction after eating certain foods - hives, itching, swelling or trouble breathing - you may have a food allergy. Then again, you might not.

Allergy Relief

Some of the medications used to treat respiratory allergy symptoms include antihistamines, decongestants, nasal sprays and eyedrops.

What do medications do?

Allegra D
Allegra
Claritin-D
Flonase
Nasacort
Nasacort AQ
Nasonex
Patanol
Zyrtec

Signs and symptoms

The most common signs and symptoms of a true food allergy include:

Hives, itching or eczema
Swelling of the lips, face, tongue and throat, or other parts of the body
Wheezing, nasal congestion or trouble breathing
Abdominal pain, diarrhea, nausea or vomiting
Dizziness, lightheadedness or fainting

In a severe allergic reaction to food, you may have more extreme versions of the above reactions, or you may experience the following life-threatening signs and symptoms:

Constriction of airways, including a swollen throat, resulting in trouble breathing
Shock, with a severe drop in blood pressure
Rapid pulse

Written and revised by

David Cohen, M.D.

Our doctors write and review articles for accuracy and keep them up to date.

health.am provides general information, not medical advice. Always consult a qualified health professional about your own health.

Food allergy

Key points

Overview

Allergy Relief

What do medications do?

Signs and symptoms

Explore health topics

More in this topic

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A new approach to treating peanut and other food allergies

Drug therapy for allergy moves forward

Food allergy

Key points

Overview

Allergy Relief

What do medications do?

Signs and symptoms

Explore health topics

More in this topic

Exposure to mercury, seafood associated with risk factor for autoimmune disease

A new approach to treating peanut and other food allergies

Drug therapy for allergy moves forward

Causes

Risk factors

When to seek medical advice

Screening and diagnosis

Treatment

Prevention