Allergy due to food
What is a food allergy? — A food allergy is when a person's immune system responds as if a certain food is harmful to the body. If a person eats or touches that food, they can have an allergic reaction. In some cases, breathing in tiny pieces of the food can also cause a reaction. Most allergic reactions happen within 5 minutes to 1 hour after eating or touching the food.
The most common foods that people are allergic to are:
Milk and foods that contain milk, such as ice cream or butter (called dairy foods)
Tree nuts, such as almonds or cashews
Shellfish, such as shrimp or oysters
People can have an allergy to one or more foods. Sometimes it is hard to tell if you really have a food allergy or not. People can feel sick after eating some foods for other reasons. For example, people can get heartburn after eating spicy foods, or have vomiting and diarrhea from food poisoning. But these are not the same as a food allergy.
What are the symptoms of a food allergy? — The symptoms of a food allergy can range from mild to severe.
Mild symptoms can include:
Hives – Raised, red patches of skin that are very itchy (picture 1)
Red or swollen skin
Itchy, watery, or swollen eyes
Runny nose or sneezing
Severe symptoms are also called "anaphylaxis." They can include:
Swelling of the throat
Wheezing, coughing a lot, or trouble breathing
Throwing up or having diarrhea
Feeling dizzy or passing out
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. Doctors can use 2 types of tests to tell if you have a food allergy. You and your doctor will decide which is best for you.
Skin test – Most skin tests involve 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.
Blood test – Blood tests for food allergies look for antibodies (proteins) called "IgEs" that the body makes when it is having an allergic response.
Your doctor or nurse will also do an exam and talk with you. Sometimes it can be hard to figure out what food you are allergic to. Keeping a record of the foods you eat and the symptoms you have is helpful.
Should I see a doctor or nurse? — Yes. If you have severe allergic symptoms, call for an ambulance (in the US and Canada, dial 9-1-1). Do not try to get yourself to the hospital.
How is a food allergy reaction treated? — The best treatment for a severe reaction is a medicine called "epinephrine." At the hospital, doctors can give you epinephrine and other medicines to treat your symptoms. Doctors will also watch to make sure your symptoms don't get worse.
Your doctor might prescribe a device called an "autoinjector" (for example, the EpiPen). This device has a shot of epinephrine that you can give yourself. If you have an autoinjector, you should keep it with you at all times. Use it right away if you think you are having a severe allergic reaction. If you are not sure how severe your reaction is, it is still better to use the autoinjector, since symptoms can get worse quickly. After you use the autoinjector, call for an ambulance. That's because the symptoms might come back and you might need more treatment in the hospital.
Your doctor might also recommend a medicine called an antihistamine such as cetirizine (sample brand name: Zyrtec) or diphenhydramine (sample brand name: Benadryl). You can get this medicine without a prescription. It can help relieve mild food allergy symptoms like itching and hives. It does not treat severe symptoms (anaphylaxis).
Can allergic reactions be prevented? — Yes. You can prevent an allergic reaction by not eating the food you are allergic to. Even a tiny bite of food can cause a big reaction. You and your doctor can make a food allergy plan that includes:
Knowing how to avoid the food you are allergic to by reading food labels
Telling restaurants about your food allergy if you eat out
Knowing when to get help for a reaction
Having an epinephrine autoinjector with you at all times
Wearing a medical bracelet to let others know about your allergy
What will my life be like? — Most people with a food allergy are able to live normal lives. But you might need to make some changes in your life. You will need to follow your food allergy plan.
You can have food allergies for your whole life. But people sometimes outgrow them. Talk with your doctor about how to tell if you have outgrown a food allergy.
Is there any way to prevent a food allergy? — It's not clear. If you have a food allergy – or your child does – you might worry that a new baby will have it, too. The baby might be at higher risk of having the same allergy. But that doesn't mean they will definitely have it. They might have the same food allergy, a different food allergy, or no food allergy at all.
If you are pregnant or breastfeeding, you might wonder whether you should avoid a certain food. For example, if you already have 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 you should 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 will have 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, and to give the food at the normal time (starting at 4 to 6 months old). 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.
All topics are updated as new evidence becomes available and our peer review process is complete.
This topic retrieved from UpToDate on: Mar 30, 2020.
Topic 15337 Version 13.0
Release: 28.2.2 - C28.105
© 2020 UpToDate, Inc. and/or its affiliates. All rights reserved.
New! No Prescription? No problem.
Affordable Online Care is here! Answer a few questions about your concern and receive a treatment plan in as little as 15 minutes, from a board-certified provider, 100% online.Learn more