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What is an allergy?
Having an allergy means that your body perceives a harmless substance (the allergen) as dangerous and is mounting an internal battle to take care of it. This hypersensitive process is called an allergic reaction.
What is an allergen?
An allergen is a substance that your body perceives as dangerous, but which a non-allergic person's body ignores. Common allergens are pollen, molds, dust mites, animal dander, certain foods and medications, and latex.
What is the difference between an allergen and an antigen?
An antigen is a substance, usually a protein that the body perceives as foreign, which sets in motion an immune response. This is the way the body fights disease. An allergen is a specific type of antigen, which sets in motion a hypersensitivity, or allergic reaction. Other types of antigens are bacteria and viruses. The difference between an allergen and other antigens is that the allergen is harmless to most people, whereas other antigens are indeed harmful.
What are antibodies?
Antibodies are proteins created by your body to fight the battle against the invader (the allergen/antigen). The first time your body encounters the antigen, some antibodies are produced. With each additional exposure, more antibodies are produced. In the beginning, you may not feel any reaction. But, as more antibodies are produced, you start to experience some symptoms of an allergic reaction.
How are allergies and asthma related?
Allergies can trigger an asthma attack, in which you may experience a feeling of tightness in the chest, difficulty breathing and wheezing. Having good control over your allergies can limit both the frequency and severity of asthma attacks.
What is an allergic reaction?
An allergic reaction is the process your body goes through when it senses the presence of an allergen. The allergen may be ingested as food or medication, inhaled through the mouth or nose, or may come in contact with the skin. When the body senses the presence of an allergen, antibodies are produced. The antibodies attach to mast cells, which release a substance called histamine. Histamine's job is to narrow the bronchial tubes in the lungs, dilate blood vessels, and produce secretions, such as mucus. Histamine is the main substance responsible for the symptoms characteristic of an allergic reaction. Medications that inhibit the release of histamines are called antihistamines. An allergic reaction is a hypersensitivity reaction to a substance to which most people do not react.
Are allergies dangerous?
Most allergies are not dangerous, although they can make life miserable! The exception is anaphylaxis, which is a life-threatening emergency requiring immediate medical attention.
Symptoms of a mild reaction
In a mild reaction, the allergy sufferer may experience localized symptoms: flushing, rash/hives, itchy or watery eyes and some nasal congestion. In a mild reaction, the symptoms do not spread to other parts of the body.
Symptoms of a moderate reaction
In a moderate reaction, symptoms become stronger and may start to spread throughout the body. Breathing may become affected, and any itchiness may spread from one part of the body to the rest of the body. A moderate reaction can signal the beginning of anaphylaxis.
Symptoms of a severe or anaphylactic reaction
Anaphylaxis is a rare, life-threatening emergency requiring immediate medical attention. In anaphylaxis, the body's response to the allergen is sudden and systemic (meaning, the whole body is involved). While any allergen can potentially lead to an anaphylactic reaction, certain foods, medications and insect stings are the most likely culprits.
Symptoms include:
- Mental confusion, dizziness (due to a drop in blood pressure)
- Swelling (especially of the face, tongue and throat), and
- Difficulty breathing.
The person's condition can deteriorate rapidly (within minutes), leading to shock and even death.
People at increased risk of anaphylaxis (who may have already had a moderate reaction to a bee sting, for example) may carry with them an emergency kit containing injectable epinephrine (also known as adrenaline), prescribed by their physician. The epinephrine helps to constrict blood vessels, raising blood pressure, reducing the risk of shock. While the individual still needs to seek emergency care, the injected epinephrine "buys some time," allowing about 15 minutes travel time to a hospital emergency department. Because the symptoms can progress so rapidly, a person suffering an anaphylactic reaction may need assistance administering the injection. If you think you could be at increased risk of anaphylaxis, speak to your doctor about prescribing such a kit. The injections also come in a "pen" form, where the needle is not visible. The "pen" is placed against a large muscle, such as the thigh. When the trigger is pushed, the needle with the epinephrine is injected into the muscle. Discuss the need to wear a MedicAlert® bracelet with your physician.
Dyes used in diagnostic testing that can precipitate an allergic reaction
There are some diagnostic tests that use an iodine contrast medium. People allergic to seafood may react to an iodine solution that is placed on the skin (topical), or taken internally, as a contrast medium. If you need to undergo such diagnostic tests, and you have seafood allergies or have had a rash after topical application of iodine be sure to discuss this with your physician. You could be at risk for anaphylaxis. Anytime you undergo diagnostic testing with a contrast medium, someone should be monitoring your blood pressure, heart rate and respiratory rate. You should mention any itchiness, agitation, nausea or other symptoms experienced during the test.
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External Sources
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American Academy of Allergy, Asthma and Immunology
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Asthma and Allergy Foundation of America
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This article was reviewed and updated June 2007.
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