Table of Contents

Topic Overview

What is a food allergy?

When you have a food allergy, your body thinks certain foods are trying to harm you. Your body fights back by setting off an allergic reaction. A mild reaction is no fun, but it isn’t dangerous. A serious reaction can be deadly. But quick treatment and emergency management can prevent death.

Allergies tend to run in families. You are more likely to have a food allergy if other people in your family have allergies like hay fever, asthma, or eczema (atopic dermatitis).

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Food allergies are more common in children than in adults. Children sometimes outgrow their food allergies, especially allergies to milk, eggs, or soy. But if you develop a food allergy as an adult, you will most likely have it for life.

Food allergy versus food intolerance

Food intolerances are much more common than food allergies. True food allergies are a reaction to food or food additives by your body’s immune system.

Many people think they have a food allergy, but in fact they have a food intolerance. Food intolerance is much more common. It can cause symptoms like an upset stomach, but it does not involve the immune system. A food intolerance does not cause an allergic reaction. A food intolerance can make you feel bad, but it is not dangerous. A food allergy can be dangerous.

What are the symptoms?

Food allergies can cause many different symptoms. They can range from mild to serious. If you eat a food you are allergic to:

- Your mouth may tingle, and your lips may swell.
- You may have a stuffy nose, wheeze, or be short of breath.
- You may have cramps, an upset stomach, or diarrhea.
- You may feel dizzy or light-headed if your blood pressure drops.
- You may have itchy skin with red, raised bumps called hives.

Kids usually have the same symptoms as adults. But sometimes a small child just cries a lot, vomits, has diarrhea, or does not grow as expected. If your child has these symptoms, see your doctor.

Some people have symptoms after eating even a tiny bit of a problem food.

The most severe reaction is called anaphylaxis (say “ANN-uh-fuh-LAK-suss”). It affects your whole body. Anaphylaxis can start within a few minutes to a few hours after you eat or are exposed to the food. And the symptoms can go away and come back hours later. Symptoms vary from person-to-person and from episode-to-episode. For example:

Your throat and tongue may swell quickly.
You may suddenly start wheezing or have trouble breathing.
You may feel sick to your stomach or vomit.
You may feel faint or pass out.

Anaphylaxis can be deadly. If you have (or see someone having) any of these symptoms, give epinephrine and call 911 right away.

What foods most often cause a food allergy?

A few foods cause most allergies. The protein in a food that causes an allergy is called a food allergen. The most common food allergies according to Health Canada are:

- Eggs
- Milk
- Mustard
- Peanuts
- Seafood (fish, crustaceans, and shellfish)
- Sesame
- Soy
- Sulphites
- Tree Nuts
- Wheat

If you are allergic to one food, you may also be allergic to other foods like it. So if you are allergic to shrimp, you may also be allergic to lobster or crab.

How is a food allergy diagnosed?

Your doctor will ask questions about your medical history and any family food allergies. And he or she will do a physical examination. Your doctor will also ask what symptoms you have. He or she may want you to write down everything you eat and any reactions you have. Your doctor will consider other possibilities that could be confused with food allergies, such as a food intolerance.

Because food allergies can be confused with other problems, it is important for your doctor to do a test to confirm that you have a food allergy. Your doctor may first start out with either skin testing or a blood test to determine what you are allergic to. But an oral food challenge is the best way to diagnose a food allergy. In an oral food challenge, you will eat a variety of foods that may or may not cause an allergic reaction. Your doctor watches to see if and when a reaction occurs.

A skin prick test can help to find out which foods will cause a reaction. The doctor will put a little bit of liquid on your skin and then prick your skin. The liquid has some of the possible food allergen in it. If your skin swells up like a mosquito bite, your doctor knows that you are allergic to that food. Your doctor may also do blood tests to look for the chemicals in your blood that cause an allergic reaction.

How is it treated?

The best treatment is to never eat the foods you are allergic to. Learn to read food labels and spot other names for problem foods. For example, milk may be listed as “caseinate,” wheat as “gluten,” and peanuts as “hydrolyzed vegetable protein.” When you eat out or at other people’s houses, ask about the foods you are served.

If you have a history of severe food allergies, your doctor will prescribe epinephrine (say “eh-puh-NEH-fren”). An epinephrine shot can slow down or stop an allergic reaction. Your doctor can teach you how to give yourself the shot if you need it.

You can have symptoms again even after you give yourself a shot. So go to the emergency room every time you have a severe reaction. You will need to be watched for several hours after the reaction.

If you have had a serious reaction in the past, your chance of having another one is high. Be prepared.

Keep epinephrine with you at all times.
Wear a medical alert bracelet to let others know about your food allergy.
Check the expiration date on the epinephrine. Replace it as needed.

If your child has a food allergy, what else should you think about?

Talk to your child’s teachers and caregivers. They should know how to keep problem foods away from your child. Teach them what to do if your child eats one of these foods by mistake.

If your child has ever had a severe reaction, keep epinephrine nearby at all times. Some kids carry their kit in a fanny pack. Have your child wear a medical alert bracelet. Teach all caregivers to act quickly. They should: