What is a food allergy?
A food allergy is a reaction by the body’s immune system to something you ate or drank. Food allergies are more common in young children and in people who have other allergies, such as hay fever and eczema (dry skin rash). Food allergies must be taken seriously. Very tiny amounts of a food can cause a reaction if you are allergic to it, and a severe reaction can be sudden and life threatening.
How does it occur?
A food allergy occurs when the body’s immune system mistakenly believes that a harmless substance (a food) is harmful. In order to protect the body, the immune system creates substances called antibodies to that food. The next time you eat that particular food, your immune system releases huge amounts of chemicals, such as histamines, to protect the body. These chemicals trigger symptoms that can affect the respiratory and cardiovascular systems, gastrointestinal tract, and skin.
Many different foods can cause an allergic reaction. The foods that most often cause a reaction are:
· cow’s milk
· tree nuts, such as walnuts and cashews
People who have asthma have an increased risk of a severe or fatal reaction.
What are the symptoms?
Reactions differ. They may happen right away or not for several hours. Symptoms may be mild, or they might be life threatening when the allergy causes breathing problems.
The symptoms of an allergic reaction depend on the type and severity of the reaction.
Common symptoms of an allergy are:
· itchy, watery eyes
· stuffy or runny nose
· swelling–for example, swelling of the eyelids
· a rash or hives (raised, red, itchy areas on the skin)
· stomach cramps
Some of the symptoms of a severe allergic reaction are:
· trouble breathing, including wheezing
· swelling of the lips, tongue, or throat
· hives (itchy, blotchy, raised rash)
· feeling dizzy or faint
· nausea, vomiting, or diarrhea
The symptoms of a severe reaction generally occur within minutes to 2 hours after contact with the food causing the reaction. In rare instances symptoms may occur up to 4 hours later.
Some fresh fruits and vegetables can cause a mild allergic reaction called oral allergy syndrome. The itching or tingling of the mouth that occurs is not a true allergy. Instead, it is the result of cross-reactivity. These foods contain some of the same proteins that are found in certain pollens that you may be allergic to. For example, if you are allergic to ragweed, you may react to eating melons and bananas. An allergy to birch pollen may cause a reaction to apples, plums, and nectarines.
How is it diagnosed?
Your primary care provider will ask about your personal and family history for allergies. You will be asked about your symptoms and the foods you eat. If your symptoms are not severe, your primary care provider may suggest that you try to find which foods cause your symptoms by not eating certain foods for a while. Then you can carefully try eating these foods again, one at a time, to see if your symptoms come back. Ask your primary care provider which foods you should avoid at first.
Your primary care provider may recommend that you keep a food diary. This involves recording all of the food you eat and drink and any symptoms you have.
If your symptoms are severe and there is no obvious cause, then it may be possible to have allergy skin tests or blood tests for common food allergies such as egg, cow’s milk, nuts, and shellfish.
How is it treated?
Mild symptoms may not need treatment. Or your primary care provider may prescribe antihistamine medicine for you to use as needed.
For moderate symptoms your primary care provider may also prescribe a steroid medicine for you to use for a few days. Using a steroid for a long time can have serious side effects. Take steroid medicine exactly as your primary care provider prescribes. Don’t take more or less of it than prescribed by your primary care provider and don’t take it longer than prescribed. Don’t stop taking a steroid without your primary care provider’s approval. You may have to lower your dosage slowly before stopping it.
For severe reactions, you will need a shot of epinephrine. You may need additional medicine, depending how severe your reaction is. You should be watched wherever you are treated for 4 to 6 hours to make sure that the symptoms do not come back after the effects of the medicine have worn off.
Once your reaction has been successfully stopped, you should ask what food or foods most likely caused the reaction. You should avoid those foods until you have follow-up with your primary provider or an allergist.
How long will the effects last?
The effects of the allergic reaction last from several minutes to hours, depending on how much of the food you ate and the severity of your allergy, and how quickly you received treatment.
Some food allergies are outgrown while others are lifelong. Most children who are allergic to milk, eggs, soy, and wheat outgrow their allergies. However, allergies to peanuts, nuts, fish, and shellfish are almost never outgrown.
How can I take care of myself and help prevent another allergic reaction to food?
The only way to not have a reaction is to avoid the food that causes the allergy symptoms. When you know you are allergic to a specific food, you should avoid eating that food. Be sure to check the ingredients on food package labels and ask about the ingredients in foods prepared in restaurants when you eat out.
If you are breast-feeding a baby that has a food allergy, stop eating or drinking the food your baby is allergic to. Food allergens can get into your breast milk.
Follow all of your primary care provider’s instructions.
Keep a record of all reactions you have to food or drink.
Substitute soy-based products for milk if you are allergic to milk but not to soy. If you are allergic to milk and soy, substitute rice milk or nut-based milk. Look for rice or nut milks that are calcium enriched.
If you tend to have severe food allergy reactions, you should ask your primary care provider about carrying medicine with you for emergency use, such as shots of epinephrine (EpiPen). Tell others about your allergy–what you need to avoid, the symptoms of an allergic reaction, and how they can help if you are having a severe reaction.Be sure to always carry your EpiPen with you.
Wear a medical ID bracelet or necklace that notes your allergy. Or you carry a card with this information in your wallet or purse.
Call 911 for emergency help if you have sudden, severe food allergy symptoms or your symptoms do not get better and you start having throat tightness or trouble breathing.
How can I keep from having a food allergy?
There is no cure for food allergy, but research is ongoing. There are studies that suggest that gradual exposure to some food allergens may allow some tolerance to that food. These challenges should be done only under medical supervision, and this possible treatment for food allergy is still being studied. The current recommendation is that the only way to keep from having an allergic reaction is to avoid the food that causes it.
Feeding babies only breast milk for the first 4 to 6 months of life is recommended to help lower the risk of food allergy.
Where can I get more information?
Visit or contact the following:
Anaphylaxis Canada for general information on allergies at: http://www.anaphylaxis.ca/
2005 Sheppard Avenue East
Toronto, Ontario M2J 5B4
Health Canada website for information on food allergies at: http://www.hc-sc.gc.ca/fn-an/securit/allerg/fa-aa/index-eng.php, information on food allergy labeling at: http://www.inspection.gc.ca/food/consumer-centre/fact-sheets/labelling-food-packaging-and-storage/food-allergies/eng/1332442914456/1332442980290, or information on severe allergic reaction at: http://www.hc-sc.gc.ca/hl-vs/iyh-vsv/med/allerg-eng.php.