Allergies Health Article

Symptoms

Symptoms depend on the specific type of allergic reaction. Allergic rhinitis is characterized by an itchy, runny nose, often with a scratchy or irritated throat due to post-nasal drip. Allergic conjunctivitis (inflammation of

the thin membrane covering the eye) causes redness, irritation, and increased tearing in the eyes. Asthma causes wheezing, coughing, and shortness of breath. Symptoms of food allergies depend on the tissues most sensitive to the allergen and whether it is spread systemically by the circulatory system. Gastrointestinal symptoms may include swelling and tingling in the lips, tongue, palate or throat, and nausea, cramping, diarrhea, and gas. Contact dermatitis is marked by reddened, itchy, weepy skin blisters.

Systemic reactions may occur from any type of allergen, but are more common following ingestion or injection of an allergen. Skin reactions include hives and angioedema (a deeper and more extensive skin reaction) involving more extensive fluid collection. Anaphylaxis is marked by airway constriction, blood pressure drop, widespread tissue swelling, heart rhythm abnormalities, and, in some cases, loss of consciousness.

Diagnosis

Allergies may often be diagnosed by taking a detailed medical history, matching the onset of symptoms to the exposure to possible allergens. Allergy tests may be used to identify potential allergens. These tests usually begin with prick tests or patch tests that expose the skin to small amounts of allergen to observe the response. Reaction will occur on the skin even if the allergen is normally encountered in food or in the airways.

RAST testing, performed by a laboratory technologist, is a blood test that measures the level of reactive IgE antibodies in the blood. Provocation tests, most commonly done with airborne allergens, present the allergen directly through the route normally involved. Food allergen provocation tests require abstinence from the suspect allergen for two weeks or more, followed by ingestion of a measured amount.

Treatment

A variety of prescription and over-the-counter drugs are available for treatment of immediate hypersensitivity reactions. Most work by decreasing the ability of histamine to provoke symptoms. Other drugs counteract the effects of histamine by stimulating other systems or reducing immune responses in general.