What Are Food Allergies?
Milk, eggs, soy, wheat, tree nuts, peanuts, fish, and shellfish are among the most common foods that cause allergies.
Young kids who have food allergies often outgrow their allergy — but not always. A lot depends on which foods someone is allergic to. Some foods are easier to outgrow than others. Fish and shellfish allergies usually develop later in life, and people are unlikely to outgrow them.
Food allergies can cause serious and even deadly reactions. So it's important to know how to recognize an allergic reaction and to be prepared if one happens.
What Are the Most Common Food Allergens?
Doctors are diagnosing more and more people with food allergies. People can be allergic to any food, but eight common allergens account for most food allergy reactions:
What Are the Signs & Symptoms of a Food Allergy?
With a food allergy, the body reacts as though that particular food product is harmful. As a result, the body's immune system (which fights infection and disease) creates antibodies to fight the food .
Every time the person eats (or, in some cases, handles or breathes in) the food, the body releases chemicals like . This triggers allergic symptoms that can include:
- trouble breathing
- throat tightness
- belly pain
- itchy, watery, or swollen eyes
- red spots
- a drop in blood pressure, causing lightheadedness or loss of consciousness (passing out)
People often confuse food allergies with food intolerance because of similar symptoms. The symptoms of food intolerance can include burping, indigestion, gas, loose stools, headaches, nervousness, or a feeling of being "flushed." But food intolerance:
- doesn't involve the immune system
- can happen because a person can't digest a substance, such as lactose
- can be unpleasant but is rarely dangerous
What Happens in a Food Allergy Reaction?
Most reactions happen pretty soon after eating a particular food. Everyone's different, though. So although two people may have peanut allergy, for example, both may not have the same type of allergic reaction. And even the same person can have different reactions to a particular food, depending on factors like how much he or she was exposed to.
- be very mild and only involve one part of the body, like hives on the skin
- be more severe and involve more than one part of the body
- happen within a few minutes or up to 2 hours after contact with the food
Food allergy reactions can affect any of these four areas of the body:
- skin: itchy red bumps (hives); eczema; redness and swelling of the face or extremities; itching and swelling of the lips, tongue, or mouth (skin reactions are the most common type of reaction)
- gastrointestinal tract: belly pain, nausea, vomiting, or diarrhea
- respiratory system: runny or stuffy nose, sneezing, coughing, wheezing, shortness of breath
- cardiovascular system: lightheadedness or fainting
Sometimes, an allergy can cause a severe reaction called anaphylaxis, even if a previous reaction was mild. Anaphylaxis might start with some of the same symptoms as a less severe reaction, but can quickly get worse. The person may have trouble breathing or pass out. More than one part of the body might be involved. If it isn't treated, anaphylaxis can be life-threatening.
How Is a Food Allergy Diagnosed?
Your doctor will look for any other conditions that could be causing symptoms. For example, if you have diarrhea after drinking milk, the doctor may check to see if lactose intolerance could be causing the problem instead of a food allergy. Another condition that may mimic food allergy symptoms is celiac disease. People with celiac disease are not able to tolerate gluten, a protein found in wheat and certain other grains.
If your doctor thinks you have a food allergy, you'll probably see an . The allergist will ask you questions again and do a physical exam (such as listening to your lungs). He or she will probably also run some tests to help diagnose the problem.
The most common kind of allergy test is a skin test. A doctor or nurse will scratch the skin (usually on the forearm or back) with a tiny bit of the extract, then wait a few minutes to see if there's a reaction. Doctors may also do other tests, including a blood test. Blood tests show if there are antibodies to a particular food in the person's blood.
If you do have a food allergy, your allergist will work with you to create a treatment plan. You'll also develop a written food allergy emergency action plan to keep at school to help you avoid a serious reaction — and to provide guidance in case you do have a reaction.
How Are Food Allergies Treated?
There's no cure for food allergies, and the only real way to treat them is to avoid the food in question. But doctors can prescribe medicines to help lessen symptoms if they do happen, and even save a person's life if the reaction is serious.
Antihistamines can treat isolated symptoms such as hives, runny nose, or abdominal pain associated with an allergic reaction.
If your doctor diagnoses you with severe allergies, he or she may prescribe epinephrine, which can be lifesaving if a person has anaphylaxis. Because it's important that the medicine get into a person's bloodstream quickly, epinephrine comes in an auto-injector.
If your doctor has prescribed epinephrine, you'll need to take the auto-injector with you everywhere you go and also keep one on hand at home, school, and any relatives' or friends' homes that you visit a lot.
So how do you know when you should use epinephrine? Your doctor will go over this with you, but signs and symptoms of anaphylaxis include:
- throat feels tight
- swelling in the mouth
- trouble breathing
- any symptoms from two or more body systems (skin, heart, lungs, etc.), such as hives and belly pain
- any other combination of two or more symptoms that affect different parts of the body
If you have to give yourself a shot of epinephrine (or someone else gives it to you), call 911 immediately after so an ambulance can take you to the hospital. This is important because sometimes there can be a second wave of symptoms. Medical staff need to watch anyone who has used epinephrine for a severe allergy in case the person needs more treatment.
Avoiding Food Allergens
If you have food allergies of any kind, you'll become an expert in reading food labels.
Makers of foods sold in the United States must state whether foods contain any of the top eight most common allergens: milk, eggs, fish, shellfish, tree nuts, peanuts, wheat, or soy.
For more information on foods to avoid, check sites such as the Food Allergy Research and Education network (FARE).
Label information helps if you're buying packaged foods, but what about when you eat away from home? If you have a food allergy, tell the people serving you know about it. Most of the time, you can't stop there: Ask what each food on a menu or in the display case contains. If the people helping you don't know, see if they can find out (from the chef or person who prepared the food).
You'll also need to be aware of other food pitfalls, such as the possibility that the food you're allergic to could get into other items from cutting surfaces, shared utensils, etc.
Coping with a food allergy can be hard. If you know someone with food allergy, show your support and understanding. Some people with food allergies may feel left out or awkward. And if you have a food allergy, let your friends know. Chances are, they'll understand and look out for you.
- Food Allergies: How to Cope
- Nut and Peanut Allergy
- Shellfish Allergy
- Milk Allergy
- Egg Allergy
- Food Allergies and Travel
- Allergy Testing
- Serious Allergic Reactions (Anaphylaxis)
- 5 Ways to Be Prepared for an Allergy Emergency
- My Girlfriend Has a Peanut Allergy. Do We Have to Worry About Kissing?
- My Friend Has a Food Allergy. How Can I Help?
- Celiac Disease
Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor.
© 1995- KidsHealth® All rights reserved.
Images provided by The Nemours Foundation, iStock, Getty Images, Veer, Shutterstock, and Clipart.com.