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 postnasal drip. Inflammation of the thin membrane covering the eye (allergic conjunctivitis) 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; nausea; cramping; diarrhea; and gas. Contact dermatitis is marked by reddened, itchy, weepy skin blisters.

Whole body or systemic reactions may occur from any type of allergen, but are more common following ingestion or injection of an allergen. Skin reactions include the raised, reddened, and itchy patches called hives. A deeper and more extensive skin reaction, involving more extensive fluid collection, is called angioedema. Anaphylaxis, another reaction, is marked by difficulty breathing, blood pressure drop, widespread tissue swelling, heart rhythm abnormalities, lightheadedness, and in some cases, loss of consciousness.

Diagnosis

Allergies can often be diagnosed by a careful medical history, matching the onset of symptoms to the exposure to possible allergens. Allergy tests can be used to identify potential allergens. These tests usually begin with prick tests or patch tests, which 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 is a blood test that measures the level of reactive 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. Provocation tests are not used if anaphylaxis is a concern due to the patient's medical history.