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Allergies Health Center

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Living With Allergies: A Glossary

Allergen. A foreign substance the body perceives as harmful, triggering an allergic reaction.

Allergist. A doctor who diagnoses and treats allergy-related conditions.

Recommended Related to Allergies

Indoor Allergy Triggers

You come home after a day away, step into the house, and the symptoms hit: Watery eyes, scratchy throat, congestion. Could it be indoor allergies? Allergies are very common. An estimated 50 million Americans are allergic to everything from dust and dander, to mold and mites. But what about you? How can you be sure you have indoor allergies -- and pinpoint what’s causing them? To help you understand what’s behind your allergy symptoms, WebMD got tips from experts on how to recognize common allergy...

Read the Indoor Allergy Triggers article > >

Anaphylaxis . A life-threatening allergic reaction involving the entire body. Anaphylaxis requires immediate medical attention.

Antihistamines . These drugs block histamine -- a chemical the body releases during an allergic reaction -- reducing symptoms such as itching, sneezing, and runny nose.

Asthma . A chronic inflammatory lung disease. Symptoms include breathing problems, fatigue, headaches, and cough. Asthma is often triggered by allergens, infection, exercise, cold air, or other factors.

Atopic dermatitis . See "Eczema."

Bronchitis . An inflammation of the lung's airways. Symptoms include a persistent cough and phlegm. Bronchitis is usually seen in smokers and in places with high pollution.

Contact dermatitis. An allergic reaction that occurs after skin comes in contact with an allergen such as poison ivy, washing powders, perfumes, or other irritants.

Dander. Small pieces of skin shed by an animal, similar to human dandruff. Proteins found in dander are the major causes of pet allergies.

Decongestants . Medications that shrink swollen nasal membranes, decreasing congestion and mucus, and making it easier to breathe.

Eczema . Chronic inflammation that causes a skin rash. Eczema may be a reaction to an allergen. Symptoms include itching, crusting, blisters, and scaling. Atopic dermatitis is a type of eczema that worsens after exposure to an allergen.

Epinephrine . A drug used to immediately treat severe allergic reactions. Also known as adrenaline. Epinephrine causes an increase in blood pressure and heart rate.

Inflammation. Redness, swelling, heat, and pain in a tissue. Such symptoms can be the result of an allergic reaction in the nose, lungs, or skin.

Hay fever . Also known as allergic rhinitis. Hay fever is an inflammation of the mucus membranes in the nose. Hay fever often results from allergies to pollen, dust, certain foods, and other substances. Symptoms include sneezing, itching, runny nose, and nasal congestion.

Histamine. A chemical released by the immune system after it's exposed to an allergen. It causes tissues to become swollen, inflamed, itchy, and red.

Hives . An allergic reaction of the skin. Symptoms include itchy, swollen, red bumps that appear suddenly. Hives can show up anywhere, including lips, tongue, and ears. Also known as urticaria.

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