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Allergy
Medical Questions » Allergy
| Name: Allergy |
| Also known as: |
| An excessive reaction to a substance which in most people causes no reaction. |
Causes of Allergy
Significant allergies occur in 10% of the population. An allergy may be triggered by almost any substance including foods, pollens, dusts, plants, animals, feathers, furs, mould, drugs, natural or artificial chemicals, insect bites and gases. Some individuals are far more susceptible to a wide range of substances than others and the tendency to develop allergies may be inherited. Allergy reactions may be very localized (eg. at the site of an insect bite, or in just one eye), may occur suddenly or gradually, may last for a few minutes or a few months, may involve internal organs (eg. lungs), or be limited to the body surface (eg. skin or nose lining). When a person is exposed to a substance to which they are allergic, the body reacts by releasing excessive amounts of histamine from mast cells that are found in the lining of every body cavity and in the skin. Histamine is required at times to fight invading substances, but when released in excess, it causes tissue inflammation and an allergic reaction. |
Symptoms of Allergy
May cause a wide range of symptoms including itchy skin and eyes, diarrhea, redness and swelling of tissues, a runny nose and skin lumps, depending on the area of the body affected. |
Tests for Allergy
Screening blood tests can determine if a patient is suffering from an allergy. An allergy to specific substance can be detected by skin or blood tests. In the skin test, a minute amount of the suspected substance is scratched into a very small area of skin and the reaction of that skin area is then checked for a reaction a day or so later. In blood tests, specific antibodies to invading allergic substances are sought and identified. |
Treatment for Allergy
Depends on where the allergy occurs, its severity, and its duration. Antihistamine drugs are the main treatment and may be given by tablet, mixture, injection, nose spray or cream, but some types may cause drowsiness. A severe attack may require steroid tablets or injections, adrenaline injections, or in very severe cases, emergency resuscitation. There are a number of medications (eg. sodium cromoglycate, steroid sprays, nedocromil sodium) that can be used on a regular basis to prevent allergic reactions. If the substance that causes an allergy can be identified, further episodes may be prevented by desensitization which involves giving extremely small doses of the allergy-causing substance to the patient by injection, and then slowly increasing the dose over many weeks or months until the patient can completely tolerate the substance.
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Complications of Allergy of its treatment
Severe allergic reactions may kill a patient by causing the throat to swell shut, acting on the heart to cause irregular beats, or inducing a critical lung spasm. A small number of highly allergic patients must carry an emergency supply of injectable adrenaline with them at all times. |
Likely Outcome of Allergy
Most allergies can be successfully treated and prevented. Some allergies can be cured by desensitization. |
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