Condition Basics

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. In most cases, the symptoms are mild—a rash or an upset stomach. A mild reaction is no fun, but it isn't dangerous. A serious reaction can be deadly. But quick treatment can stop a dangerous reaction.

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.

Many people think they have a food allergy, but in fact they have food intolerance. An intolerance can cause some of the same symptoms as a mild food allergy, like an upset stomach. It can make you feel bad, but it isn't dangerous.

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. But a food intolerance doesn't cause an allergic reaction.

What causes it?

Food allergies occur when your body's immune system overreacts to substances in food you have eaten. This triggers an allergic reaction. Food allergies are more common in young children than in adults.

• Milk, eggs, peanuts, tree nuts, fish, shellfish, wheat, and soy cause most problems in children. Some babies are so sensitive to these foods that if the food is eaten by the mother, drinking her breast milk can cause a reaction. Most children outgrow allergies to eggs, milk, wheat, and soy.
• Peanuts, tree nuts, fish, and shellfish cause most of the allergic reactions in teens and adults. Adults typically remain allergic to the food for life.

If you are highly sensitive to a certain food, you may have an allergic reaction just by being near where the food was prepared or served.

What are the symptoms?

Food allergies can cause many different symptoms. They can range from mild to serious. A mild reaction may include tingly lips, a stuffy nose, dizziness, and a few raised, red, itchy patches of skin (called hives).

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 the food. The symptoms can go away and come back hours later. A severe reaction may cause hives all over, swelling in the throat, trouble breathing, nausea or vomiting, or fainting.

How is it diagnosed?

Your doctor will ask questions about your past health and family food allergies. And he or she will do a physical exam. Your doctor will also ask what symptoms you have when you eat certain foods.

Because food allergies can be confused with other problems, your doctor may do some tests. You may have either skin testing or a blood test. These tests help to see what you are allergic to. An oral food challenge is another way to diagnose a food allergy. 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.

How are allergic reactions to food treated?

The best treatment for allergic reactions to food is to avoid the food that causes the allergy. When that isn't possible, you can use medicines such as antihistamines for mild reactions and epinephrine for serious reactions. Epinephrine is a shot that you can give yourself when needed.

Cause

Food allergies occur when your body's immune system overreacts to substances in food you have eaten. This triggers an allergic reaction. Food allergies are more common in young children than in adults.

• Milk, eggs, peanuts, tree nuts, fish, shellfish, wheat, and soy cause most problems in children. Some babies are so sensitive to these foods that if the food is eaten by the mother, drinking her breast milk can cause a reaction. Most children outgrow allergies to eggs, milk, wheat, and soy.
• Peanuts, tree nuts, fish, and shellfish cause most of the allergic reactions in teens and adults. Adults typically remain allergic to the food for life.

Food allergies are most common in people who are atopic. This means that a tendency to have allergies runs in their family. They are more likely to have asthma, other allergies like hay fever, and a skin condition called atopic dermatitis. Asthma can make the reaction to a food more severe.

If you are very sensitive to a certain food, you may have an allergic reaction just by being near where the food was prepared or served.

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What Increases Your Risk

You have a greater chance of developing food allergies if you:

• Have a family history of allergy. If both of your parents have allergies, you are more likely to have allergies.
• Have another allergic condition such as atopic dermatitis or asthma.
• Are young. Infants and children have more food allergies than adults.
• Have a medical condition that makes it easier for allergens to pass through the walls of the stomach and intestines and enter the bloodstream. These conditions include gastrointestinal disease, malnutrition, prematurity, and diseases that impair the immune system, such as eosinophilic esophagitis (EoE).

You have a greater risk for a life-threatening allergic reaction (anaphylaxis) from food allergy if you:

• Have asthma.
• Develop allergy symptoms within minutes of eating the food.

If you or your child has a severe food allergy, always carry epinephrine and know how to use it. You should also wear a medical alert bracelet at all times. Being prepared to immediately deal with a severe allergic reaction reduces the risk of death.

Prevention

Food allergies often occur in people who have a family history of asthma, atopic dermatitis, or allergies to pollen, mould, or other substances. In most cases, allergies cannot be prevented in people who have a family history of allergic conditions.

There isn't enough proof to recommend that people who are at risk for allergies should avoid common foods that cause allergies like milk, eggs, peanuts, tree nuts, soy, wheat, fish, shellfish, and sulphites. Avoiding these foods doesn't seem to prevent allergies.

If your doctor thinks your baby might be at risk for a peanut allergy, ask him or her about introducing peanut products. There may be a way to prevent peanut allergies.^{footnote 1}

If you are a woman with a food allergy who is planning on a pregnancy and breastfeeding, talk to a dietitian, public health nurse, or your doctor. Canadian experts do not recommend avoiding certain foods during your pregnancy as a way to prevent the baby from having food allergies.^{footnote 2}

Canadian experts recommend that all babies be breastfed for up to two years or longer.^{footnote 2} Start foods that might cause allergies around 6 months of age.^{footnote 2} Most allergic reactions in children are caused by eggs, milk, wheat, soy, and peanuts. Canadian experts don't recommend trying a hydrolyzed milk formula to prevent allergies in babies. ^{footnote 2}

Tobacco smoke can make allergies worse, so it is important to have a smoke-free environment.

Preventing food allergy reactions

If you have a food allergy, you can take steps to avoid having reactions to that food. Most important, avoid eating the foods you're allergic to. Learn to read food labels and spot other names for problem foods. When you eat out or at other people's houses, ask about the foods you are served. And you can bring safe substitutes from home.

It's smart to teach your family members, co-workers, and friends what to do if you eat a food that you're allergic to.

Also, you can wear medical alert jewellery that lists your allergies.

Symptoms

Symptoms of a food allergy can affect many parts of your body, including your:

Digestive system.

Symptoms include stomach cramps, nausea, vomiting, diarrhea, itching in the mouth and throat, and rectal bleeding (rare in adults). These symptoms occur more often in children than in adults.

Skin.

Symptoms include hives or welts, swelling, itching, and redness. Skin reactions are common in children. If your baby has atopic dermatitis, you may help prevent peanut allergies by introducing peanut products early.

Respiratory system.

Symptoms include coughing, wheezing, sneezing, trouble breathing, and an itchy, stuffy, runny nose.

Children usually have the same symptoms as adults. Symptoms of milk or soy allergies in children may include eczema.

Symptoms vary from mild to life-threatening. They can appear from within minutes to days after eating a food. The most severe reaction is anaphylaxis. It affects many body systems and can be deadly.

Anaphylaxis can start within a few minutes to a few hours after you eat the food. And the symptoms can go away and come back hours later. Common triggers for anaphylaxis are peanuts, nuts, and seafood. In children, peanuts cause anaphylaxis more often than other foods. Aspirin, exercise, or alcohol can increase the risk for anaphylaxis.

What Happens

When you eat a food that triggers an allergic reaction, your body's immune system sees the food as a foreign substance (allergen). Your body reacts by making antibodies against the food. When you eat the food again, the antibodies attack the allergen. They release chemicals that cause the symptoms of an allergic reaction.

When to Call a Doctor

Give an epinephrine shot (or use your EpiPen) if:

• You think you are having a severe allergic reaction.
• You have symptoms in more than one body area, such as mild nausea and an itchy mouth.

After giving an epinephrine shot, call 911, even if you feel better.

Call 911 if you have:

• Rapid swelling of the throat or tongue.
• Trouble breathing, are wheezing, or have a deep cough, a pale face, or blue lips or earlobes.
• Severe belly pain, nausea, vomiting, or diarrhea.
• Signs of shock, including:
  • Light-headedness or a feeling that you are about to pass out.
  • Restlessness, confusion, or a sense of impending doom.
  • Moist, cool skin, or heavy sweating.
  • Weakness or thirst.
• Been given an epinephrine shot, even if you feel better.

If you see someone having a severe allergic reaction and the person becomes unconscious, call 911 or other emergency services immediately.

If your food allergy symptoms are getting worse, call your doctor. It's important to know which foods are to blame so that you can avoid them.

Watchful waiting

If your food allergy symptoms don't get worse or aren't too severe or bothersome, you can try removing suspect foods from your diet to see if symptoms disappear.

Examinations and Tests

To diagnose a food allergy, your doctor will start with a medical history and a physical exam. Your doctor may ask:

• What symptoms you have.
• If your family has any food allergies.
• How soon the symptoms began after eating food.
• If over-the-counter medicines helped.
• If other people also got sick.
• How the food was prepared.
• If you ate any other foods.

It's important to find out whether you have a food allergy or food intolerance. Your doctor may ask you to keep a record of all the foods you eat and any reactions you have to them. Your doctor will also consider if your reaction could have been caused by things like allergies to medicines or insect stings, foodborne illness, irritants in foods, or exposure to skin irritants.

Your doctor may ask you to try an oral food allergy challenge, an elimination diet, or both.

Oral food allergy challenge.

You 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. This test is considered the best way to diagnose a food allergy.

Elimination diet.

You avoid eating foods that may be causing an allergic reaction and see if your symptoms go away. If symptoms come back when you eat the food again, your doctor can confirm your food allergy. The elimination diet can last from 2 to 8 weeks.

You may also have allergy tests, such as skin tests or blood tests, to find out which foods you are allergic to.

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Treatment Overview

The best treatment for allergic reactions to food is to avoid the food that causes the allergy. When that isn't possible, you can use medicines. Antihistamines are used for mild reactions, and epinephrine for serious reactions.

For mild allergic reactions, people often try over-the-counter antihistamine and corticosteroid medicines first. Bronchodilators may also be used. They relax the airways of the lungs, making it easier to breathe. You can try prescription medicines if over-the-counter medicines don't control allergy symptoms or if they cause side effects.

If you have a severe allergic reaction, you may need a shot of epinephrine. This will relax the muscles that help you breathe. If your doctor has prescribed epinephrine, always keep it with you. Your doctor or pharmacist will teach you how to give yourself a shot if you need it. Talk to your doctor about an anaphylaxis (say "ann-uh-fuh-LAK-suss") action plan.

Self-Care

The best treatment for food allergies is to avoid the food that causes the allergy.

Talk to your doctor about an anaphylaxis (say "ann-uh-fuh-LAK-suss") action plan.

If your doctor has prescribed epinephrine, always keep it with you. It's important to give the epinephrine shot right away. Your doctor or pharmacist will teach you how to give yourself a shot if you need it. Be sure to check the expiration dates on the medicine, and replace the medicine as needed.

It's a good idea for you to wear a medical alert bracelet or other jewellery that lists your food allergies.

If you are travelling to another country, learn the words for the foods that trigger your allergy so that you can ask in restaurants and read food labels. Call airlines, tour operators, and restaurants ahead of time to explain your food allergy and request safe meals. Prepare your own food when possible. Discuss your travel plans with your doctor.

Children and food allergies

It's important to take special care with children who have food allergies. A child with severe food allergies may have a life-threatening anaphylactic reaction to even a tiny amount of a food allergen.

Make sure that all caregivers (school administrators, teachers, friends, coaches, and babysitters):

• Know about your child's food allergy.
• Can recognize the symptoms of a food allergy.
• Know where the epinephrine shot is kept and how to use it.
• Know to call 911 immediately.

Children may have only mild symptoms in the first few minutes after they eat the food allergen, but they may have severe symptoms in 10 to 60 minutes. Children always should be observed in a hospital for several hours after a reaction.

Make sure that your child:

• Always wears a medical alert bracelet.
• Always carries epinephrine. Children at risk of severe allergic reactions should keep their epinephrine at school or daycare and at home. Older, mature children should be taught to give themselves the shot.

Although your child needs to avoid certain foods, he or she still needs to eat healthy foods. A dietitian can tell you which foods are important for your child's health.

Medicines

Medicine is used to treat some food allergies.

For mild allergic reactions, people often try non-prescription medicines first. You can try prescription medicines if over-the-counter medicines don't control allergy symptoms or if they make you drowsy or cause other side effects that bother you.

For a severe allergic reaction, you may take:

• Epinephrine. It's given as a shot. It acts quickly to relax the muscles that help you breathe. You may need more than one shot if symptoms don't go away. It's used to treat anaphylaxis.
• Antihistamines. They block the action of histamine during an allergic reaction. They help improve symptoms like itching and sneezing.
• Corticosteroids. They help reduce inflammation.

For mild food allergy symptoms, you may take:

• Antihistamines and corticosteroids. They can be used for hives, belly symptoms, or sneezing and a runny nose.
• Bronchodilators for asthma symptoms. They relax the airways of the lungs and make it easier to breathe.

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