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. A severe reaction can be sudden and life threatening.
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:
People who have asthma have an increased risk of a severe or fatal reaction.
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:
Some of the symptoms of a severe allergic reaction are:
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.
Your healthcare 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 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 provider which foods you should avoid at first.
Your healthcare provider may recommend that you keep a food diary. This involves recording all of the food you eat and drink, when you eat or 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.
Mild symptoms may not need treatment. Or your healthcare provider may prescribe antihistamine medicine for you to use as needed.
For moderate symptoms your 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 healthcare provider prescribes. Don’t take more or less of it than prescribed by your provider and don’t take it longer than prescribed. Don’t stop taking a steroid without your 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 healthcare provider or an allergist.
The effects of the allergic reaction last from several minutes to hours, depending on how much of the food you ate, 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.
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.
