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Food Allergy
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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. The foods that most often cause allergic reactions are:
People who have asthma have an increased risk of a severe or fatal reaction. What are the symptoms? Reactions differ. They may occur right away or not for several hours. Symptoms may be mild, or they might be life threatening when the allergy causes breathing problems. Symptoms may include:
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. How is it diagnosed? Your health care provider will ask 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 by one, to see if your symptoms come back. Ask your provider which foods you should avoid at first. Your health care provider may recommend that you keep a food diary. This involves recording all of the food you eat and when you eat it. You should also record any symptoms you may have. If your symptoms are severe and there is no obvious cause, then it may be possible to have allergy skin tests for common food allergies such as egg, cow's milk, nuts, and shellfish. How is it treated? There is no cure for food allergy. Strict avoidance of foods you are allergic to is the only way to prevent a reaction. If you have sudden, severe food allergy symptoms or your symptoms do not get better and you start having throat tightness or trouble breathing, call 911 for emergency help. For severe reactions, you may need a shot of epinephrine. Mild symptoms may not need treatment. Or your health care provider may prescribe antihistamines for you to use as needed. For moderate symptoms your provider may also prescribe a steroid medicine for you to use for a short time. If you have had one or more severe reactions to food, ask your provider if you should carry injectable epinephrine (EpiPen) with you. A shot with the EpiPen given by yourself or a friend can slow down a severe reaction while you wait for medical help to arrive. 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. 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 an allergic reaction to food?
Hay fever is usually an allergic reaction to pollens of trees, grasses, and weeds. Sometimes it is an allergy to mold spores. Hay fever may occur any time of the year. It generally occurs in the spring, summer, or fall. Hay fever is also called seasonal allergic rhinitis. How does it occur? Allergic symptoms result from reactions of your body to substances that it sees as foreign. Substances that cause an allergic reaction are called allergens. The allergens that cause hay fever are pollen and mold. They float in the air and are spread by the wind. The type of pollen in the air depends on the growing season and area of the country. Tree pollens cause most spring hay fever. In the summer, grass and some weed pollens are usually the cause. From late summer to the first frost, other weed pollens cause hay fever. The parts of the body that may be affected by hay fever are the eyes; the lining tissue of the nose, sinuses, and eustachian tube (which connects the middle ear with the back of the throat); and, less often, the lungs. When the pollen or molds come into contact with these tissues in an allergic person, cells in the tissues release a chemical called histamine. Histamine causes the tissues to itch, swell, and produce more mucus or tears than is normal. As many as 1 in 10 people suffer from hay fever at some time in their lives. Hay fever is more common in people with other allergic conditions such as asthma or eczema. Hay fever tends to run in families. What are the symptoms? Common symptoms of hay fever are:
Other symptoms are:
How is it diagnosed? Your health care provider will ask about your history of symptoms. If your symptoms occur just in certain seasons, your health care provider will suspect that you have hay fever. A check of your ears, nose, throat, and lungs may confirm the diagnosis. Because the treatment for most cases of hay fever is the same, regardless of what you are allergic to, allergy testing is usually not necessary unless you need allergy shots. How is it treated? If you know what you are allergic to--pollens, for example--you can try to avoid the allergens. For example, using an air conditioner rather than an attic or window fan lessens the amount of pollen that gets into your home. Many hay fever symptoms are so mild that they need no treatment. Or you may just need to take a nonprescription medicine once in a while. If you need further treatment, a variety of medicines are available, such as decongestants, antihistamines, and steroid nasal sprays. Decongestants shrink the swollen lining tissues of the ear, nose, and sinuses. Possible side effects of decongestants are trouble sleeping, rapid heart rate, and elevated blood pressure. Antihistamines fight the effects of histamine on your tissues. You may need to take these medicines only when your symptoms are bothering you. In more severe cases, you might take them daily during your allergy season(s) to prevent symptoms. There are different types of antihistamines. Drowsiness is a common side effect of many antihistamines. This may not be a problem if a dose at bedtime is all you need. Or you might try the medicine for several days despite the drowsiness. Often the drowsiness goes away after you have taken the drug for 3 to 5 days. Some "nonsedating" antihistamines are available that usually don't cause drowsiness. They work well for most people, but they tend to cost more than other antihistamines. It is safe to take antihistamines and decongestants together unless you have had a bad reaction from taking either type of medicine. If antihistamines do not help eye symptoms caused by your allergy, your health care provider may prescribe eye drops. Prescription nose sprays containing steroid medicine are very effective in preventing or minimizing nasal and sinus congestion, runny nose, and postnasal drainage. A nonprescription nose spray containing cromolyn is also very effective. These nose sprays work best to relieve symptoms if you use them on a regular basis during the allergy season. Other nonprescription nose sprays with the active ingredient oxymetazoline, such as Afrin, may actually make nasal congestion worse after several days of use. This type of spray is not recommended. Symptoms that affect your breathing are treated with medicines used to treat asthma, such as:
If your symptoms bother you a lot despite medicines or if you often have complications, such as ear or sinus infections or asthma attacks, your health care provider may suggest allergy shots. You will need tests for specific allergies. For most people the best tests are skin scratch or prick tests. For these tests a health care provider places tiny amounts of suspected allergens under your skin and looks for reactions. These allergy tests may find which allergens are causing your symptoms. For your allergy shots, a mixture is prepared that contains the allergens identified in your allergy tests. The mixture is injected into your skin in tiny but increasing amounts over the course of many months. Over time, the shots make you less sensitive to the allergens. Usually after 4 to 6 months of allergy shots you will begin to have relief from your allergies. However, you will probably need to continue the shots for 2 to 3 years or longer. How long will the effects last? Allergies last different amounts of time for each person. Allergies can develop at any age. Children with hay fever may continue to have seasonal allergies as they grow older or the allergies may go away over time. If you start having allergies as an adult, you will probably continue to have them. However, the allergies may stop if you move to an area where the substances causing your allergies are not present. How can I help myself?
What can be done to help prevent hay fever? There is no known way to prevent allergies. However, some research has shown that breast-fed babies may be less likely to develop allergies and asthma. Also, if your family has a very strong history of allergies, you might try to avoid your family's most common allergens. For example, you might need to stay away from cats. This might help stop you from developing severe symptoms.  Disclaimer: This content is reviewed periodically and is subject to
change as new health information becomes available. The
information provided is intended to be informative and educational and is not a
replacement for professional medical evaluation, advice, diagnosis or
treatment by a healthcare professional.
HIA File ALL3110F.HTM Release 9.0/2006. Copyright © 2006 McKesson Corporation and/or one of its subdiaries. All Rights Reserved.
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