Patient education: Food allergy (The Basics)

Written by the doctors and editors at UpToDate

Please read the Disclaimer at the end of this page.

What is a food allergy? —

A food allergy is when the immune system acts like a certain food is harmful to the body. The immune system is the body's infection-fighting system.

Most often, allergic reactions happen from eating the food or something that contains the food. Touching the food can also cause a skin reaction.

The most common food allergies are to:

●Milk and foods that contain milk, like ice cream and butter (called dairy foods)

●Eggs

●Wheat

●Soy

●Peanuts

●Tree nuts, like walnuts or cashews

●Fish

●Shellfish, like shrimp or oysters

●Sesame

People can have an allergy to 1 or more foods.

Sometimes, it is hard to tell if you really have a food allergy or not. Some people have an "intolerance" to a food and get symptoms like stomach problems after eating it. But this is not the same as a food allergy.

What are the symptoms of a food allergy? —

With "classic" food allergies, also called "IgE-mediated" food allergies, common symptoms include:

●Hives, which are raised or puffy areas of skin that are itchy (picture 1 and picture 2)

●Flushing

●Swelling, especially of the face, eyelids, or lips (picture 3 and picture 4)

●Trouble breathing, noisy breathing (wheezing), or coughing

●Nausea, vomiting, or diarrhea

●Feeling dizzy or passing out

●Looking sick, seeming sleepier than usual, or not acting normally (in babies and young children)

The above symptoms often start quickly, usually minutes to 1 hour after having milk.

When an allergic reaction is more severe, it is called "anaphylaxis." This can make you very sick, very quickly. If not treated, it can lead to death. But this is rare.

Symptoms can differ from person to person. Also, a person can have different symptoms each time they have an allergic reaction.

Is there a test for food allergy? —

Yes. Your doctor or nurse will ask about your symptoms. You might need to see an allergy specialist, called an "allergist."

Your doctor can order tests such as:

●Blood test – This looks for proteins the body makes when having an allergic response to a food. These proteins are called "IgE antibodies."

●Skin test – This involves pricking your skin with a device that contains a tiny amount of a food. If you get a red, itchy bump, like a mosquito bite, it means you are allergic to that food. Some devices can test for several different food allergies at once.

Sometimes, it can be hard to figure out what food you are allergic to. It can help to keep a record of what you eat and any symptoms you have.

If the doctor still cannot tell if you or your child has a food allergy, they might order a test called an "oral food challenge." This involves eating a small serving of the food and gradually eating more to see if it causes symptoms. For safety reasons, this is only done in a doctor's office or hospital.

Can a food allergy be cured? —

As of now, there is no cure for a food allergy. But there are treatments that might help. These include:

●Oral immunotherapy ("OIT") – This involves getting small amounts of the food in a controlled way. You start treatment in a clinic or hospital, where you can be monitored and treated if you have a reaction. Then, you continue to take daily doses at home. The goal is to increase the "dose" of the food very slowly over time, so your immune system does not react to it. Each dose increase is done in the clinic or hospital.

●Omalizumab (brand name: Xolair) – This medicine comes as a shot. You start treatment in a clinic or hospital, where you can be monitored and treated if you have a reaction. Then, you get a shot every 4 weeks. After your first shot, you might be able to give yourself the rest of the shots at home.

Getting treatment regularly might make you less likely to have a reaction if you are accidentally exposed to the food you are allergic to.

Both OIT and omalizumab come with risks. They are not likely to make an allergy go away completely, and most people need to continue to avoid the food they are allergic to. But they might be an option in certain situations. If you want to learn more about them, talk with your doctor or nurse.

How are allergic reactions treated? —

Severe allergic reactions are treated with medicine called epinephrine. Ambulance crews and doctors can give it. People who had anaphylaxis before often get a prescription for epinephrine. It comes in 2 forms:

●A device called an "autoinjector" (sample brand names: Auvi-Q, EpiPen), which is a shot you can give yourself (figure 1)

●A spray that goes in the nose (brand name: neffy) (figure 2)

If your doctor prescribes epinephrine:

●They will show you how to use it.

●They will give you instructions for when to use it.

●Keep it with you at all times. Most doctors recommend carrying 2 doses in case you need a second dose. You might need a second dose if:

•Your symptoms do not go away completely.

•Your symptoms go away, but then start to come back.

•You used an autoinjector that did not work correctly the first time.

Call for an ambulance (in the US and Canada, call 9-1-1):

●After you use epinephrine – The medicine does not last very long in the body. Symptoms can sometimes come back as the medicine wears off. In the hospital, doctors can watch you and give you more medicine if needed.

●If you think someone is having anaphylaxis, and you do not have epinephrine

Your doctor might also recommend an antihistamine, such as cetirizine (sample brand name: Zyrtec). You can get these without a prescription. They can help relieve mild food allergy symptoms like itching and hives. They do not treat anaphylaxis.

How can I prevent an allergic reaction? —

The best way is to completely avoid the food you are allergic to. Even a tiny bite that contains the food can cause a big reaction.

●To know whether a food contains the food you are allergic to, read its ingredient label. Some countries (including the US) have laws that make companies clearly list whether a food has certain common allergens in it.

●Some foods have warning labels for food allergies, such as "May contain milk." These might have been made on machines or in factories that are also used for other foods that contain the food you are allergic to. Talk to your doctor about whether you should avoid these foods.

●If you eat at a restaurant, bakery, or ice cream shop, tell your server about your allergy.

●Non-food items can also have certain foods in them, such as eggs or wheat. These include medicines, vaccines, cosmetics, and craft supplies. Most countries (including the US) do not have laws that make companies list if these items have potential allergens in them. If you think you are allergic to any non-food items, talk to your doctor about how to avoid them.

What else should I know? —

People with a food allergy:

●Can have an allergic reaction if they share saliva with (kiss) someone who ate the food and did not brush their teeth after

●Can get hives on their skin if they touch the food

●Could have an allergic reaction by breathing in tiny pieces of the food in water droplets – This can happen when cooking or baking with the food.

●Can wear a medical alert bracelet or necklace to tell others about their milk allergy – If you cannot wear a bracelet or necklace, you can carry a document called an "allergy passport" or "allergy card."

Your doctor or nurse might have you work with a dietitian (food/nutrition expert). They can help you learn how to:

●Avoid the food you are allergic to

●Use other foods in place of the food you are allergic to

●Make sure you get the nutrients you need

What if my child has a food allergy? —

Tell their caregivers, schools, and camps. You should:

●Tell them which foods your child can and cannot eat.

●Make a plan so they know how to treat an allergic reaction.

●Make sure they know where your child's epinephrine is, and how and when to use it.

●Make sure they know how to reach you or your child's doctor in case of an emergency.

Will my child outgrow their food allergy? —

Maybe. With certain foods, like wheat, many children grow out of their allergy. For other foods, like seafood, most children do not outgrow their allergy. Your child's doctor will monitor their allergy over time to see whether they outgrow it.

Is there any way to prevent a food allergy? —

It's not clear. If you or your child has a food allergy, you might worry a new baby will have it, too. Food allergy is not common, even for babies who have a sibling or parent with a food allergy. The baby might be a little more likely to have the same or another food allergy. But usually, they have no food allergy at all.

If you are pregnant or breastfeeding, you might wonder if you should avoid a certain food. For example, if you already have a child with a milk allergy, should you stop drinking milk to reduce your new baby's risk of allergy? In most cases, the answer is probably not. But talk to your doctor to make sure you are eating a healthy diet for your situation.

When your baby is old enough to start eating solids, you need to decide when to offer the food. Doctors used to think it was better to delay this if a baby was at high risk for allergy. Now, they think it is better not to wait until the baby is older. In fact, giving the food at the normal time (starting at 4 to 6 months old) might make it less likely that they will have a food allergy. But there is still no way to know for sure if your baby will have an allergy. Your baby's doctor can help you decide when and how to offer certain foods.

Where can I learn more? —

You can get more information about food allergies from Food Allergy Research & Education ("FARE") at www.foodallergy.org.

خرید پکیج

Patient education: Food allergy (The Basics)