Conjunctivitis: Also called "pinkeye." Conjunctivitis is an inflammation of the conjunctiva, the tissue that lines the inside of the eyelid.
Dander, animal: Tiny scales shed from animal skin or hair. Dander floats in the air, settles on surfaces and makes up much household dust. Pet dander is a classic cause of allergic reactions.
Decongestant: Medication that shrinks swollen nasal tissues to relieve symptoms of nasal swelling, congestion, and mucus secretion.
Dermatitis: Inflammation of the skin, either due to direct contact with an irritating substance or to an allergic reaction. Symptoms include redness, itching, and sometimes blistering.
Drug allergy: Allergic reaction to a specific medication. The most common cause of drug allergies is penicillin.
Dust mites: Microscopic insects that live in household dust and are common allergens. Dust mites live on dead skin cells and can be found in large numbers in mattresses, pillows, carpets, curtains, and furniture.
Elimination diet: A diet in which certain foods are temporarily discontinued from the diet to rule out the cause of allergy symptoms. Sometimes, dietary changes are permanent for conditions such as celiac and a persisting food allergy.
ELISA (enzyme-linked immunosorbent assay): Blood test used to identify the substances that are causing your allergy symptoms and to estimate a relative sensitivity.
Epinephrine: A form of adrenaline medication used to treat severe allergic reactions, such as anaphylactic shock or insect stings. It is available in a self-injectable form or can be injected by a health care provider.
Food allergy: Allergy that occurs when the immune system responds inappropriately to a specific food protein that is not otherwise harmful to the body.
Hay fever: Allergic reaction caused by the pollens of ragweed, grasses, and other plants whose pollen is spread by the wind.
HEPA: High-efficiency particulate air (HEPA) filter, which removes particles in the air by forcing it through screens containing microscopic pores.
Histamine: A naturally occurring substance that is released by the immune system after being exposed to an allergen. Histamine is responsible for many of the symptoms of an allergy.
Hives: See Urticaria.
Hypoallergenic: Products formulated to contain the fewest possible allergens.