An allergy is a reaction of your immune system to something that does not bother most other people. People who have allergies often are sensitive to more than one thing. Substances that often cause reactions are
- Dust mites
- Mold spores
- Pet dander
- Insect stings
How do you get allergies? Scientists think both genes and the environment have something to do with it. Normally, your immune system fights germs. It is your body's defense system. In most allergic reactions, however, it is responding to a false alarm.
Allergies can cause a runny nose, sneezing, itching, rashes, swelling or asthma. Symptoms vary. Although allergies can make you feel bad, they usually won't kill you. However, a severe reaction called anaphylaxis is life-threatening.
Asthma is a chronic disease that affects your airways. Your airways are tubes that carry air in and out of your lungs. If you have asthma, the inside walls of your airways become sore and swollen. That makes them very sensitive, and they may react strongly to things that you are allergic to or find irritating. When your airways react, they get narrower and your lungs get less air. This can cause wheezing, coughing, chest tightness and trouble breathing, especially early in the morning or at night.
When your asthma symptoms become worse than usual, it's called an asthma attack. In a severe asthma attack, the airways can close so much that your vital organs do not get enough oxygen. People can die from severe asthma attacks.
Asthma is treated with two kinds of medicines: quick-relief medicines to stop asthma symptoms and long-term control medicines to prevent symptoms.
Food allergy is an abnormal response to a food triggered by your body's immune system. Allergic reactions to food can sometimes cause serious illness and death. Tree nuts and peanuts are the leading causes of deadly allergic reactions called anaphylaxis.
In adults, the foods that most often trigger allergic reactions include
- Fish and shellfish, such as shrimp, lobster and crab
- Tree nuts, such as walnuts
Problem foods for children are eggs, milk (especially in infants and young children) and peanuts.
Sometimes a reaction to food is not an allergy. It is often a reaction called "food intolerance". Your immune system does not cause the symptoms of food intolerance. However, these symptoms can look and feel like those of a food allergy.
Each spring, summer, and fall, trees, weeds and grasses release tiny pollen grains into the air. Some of the pollen ends up in your nose and throat. This can trigger a type of allergy called hay fever.
Symptoms can include
Taking medicines, using nasal sprays and rinsing out your nose can relieve symptoms. Allergy shots can help make you less sensitive to pollen and provide long-term relief.
- Sneezing, often with a runny or clogged nose
- Coughing and postnasal drip
- Itching eyes, nose and throat
- Dark circles under the eyes
Hives are red and sometimes itchy bumps on your skin. An allergic reaction to a drug or food usually causes them. Allergic reactions cause your body to release chemicals that can make your skin swell up in hives. People who have other allergies are more likely to get hives than other people. Other causes include infections and stress.
Hives are very common. They usually go away on their own, but if you have a serious case, you might need medicine or a shot. In rare cases, allergic reactions can cause a dangerous swelling in your airways, making it hard to breathe - which is a medical emergency.
Indoor Air Pollution
We usually think of air pollution as being outdoors, but the air in your house or office could also be polluted. Sources of indoor pollution include
- Biological contaminants like mold and pollen
- Tobacco smoke
- Household products and pesticides
- Gases such as radon and carbon monoxide
- Materials used in the building such as asbestos, formaldehyde and lead
Sick building syndrome occurs when several people are affected, but no specific source of the illness is found. Indoor air quality problems usually only cause discomfort, and most people feel better as soon as they eliminate the source of the pollution. However, some pollutants can cause diseases that show up much later, such as respiratory diseases or cancer. Making sure that your building is well-ventilated and eliminating pollutants can improve the quality of your indoor air.
Allergy tests are any of several tests used to determine the substances to which a person is allergic.
How the Test is Performed
There are many methods of allergy testing. Among the more common are:
- Skin tests
- Elimination-type tests
- Blood tests (including the radioallergosorbent, or RAST, test)
Skin tests are the most common. Specific methods vary.
One of the most common methods is the prick test. This test involves placing a small amount of suspected allergy-causing substances on the skin, usually the forearm, upper arm, or the back. Then, the skin is pricked so the allergen goes under the skin's surface. The health care provider closely watches the skin for signs of a reaction, usually swelling and redness of the site. Results are usually seen within 20 minutes. Several allergens can be tested at the same time.
A similar method involves injecting a small amount of allergen into the skin and watching for a reaction at the site. This is called an intradermal skin test.
Skin tests are most useful for diagnosing:
- Insect bite allergies
- Mold, pollen, animal, and other allergies that cause allergic rhinitis and asthma
- Penicillin allergy
Allergies to penicillin and closely related medications are the only drug allergies that can be tested using skin tests. Skin tests for allergies to other drugs can be dangerous.
The prick skin test may also be used to diagnose food allergies. Intradermal tests are not used to test for food allergies because of high false positive results and the danger of causing a severe allergic reaction.
An elimination diet can be used to check for food allergies. An elimination diet is one in which foods that may be causing symptoms are removed from the diet for several weeks and then slowly re-introduced one at a time while the person is watched for signs of an allergic reaction.
Another version of this diet is the double-blind test. This method involves giving foods and harmless substances in a disguised form. The person being tested and the provider are both unaware of whether the substance tested in that session is the harmless substance or the suspected food. A third party knows the identity of the substances and identifies them with some sort of code. This test requires several sessions if more than one substance is under investigation.
While the double-blind strategy is useful and practical for mild allergic reactions, it must be done carefully in individuals with suspected severe reactions to foods. Blood tests may be a safer first approach.
Blood tests can be done to measure the amount of immunoglobulin (Ig) E antibodies in the blood. This test may be used when skin testing is not helpful or cannot be done
Other blood tests include:
- Absolute eosinophil count
- Blood differential
- Serum immunoglobulin electrophoresis
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