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A substance that your body perceives as foreign and harmful; initiates the allergic reaction.

Allergic rhinitis

See hay fever.


Severe, life-threatening allergic response that may be characterized by symptoms such as lowered blood pressure, wheezing, vomiting or diarrhea, and swelling and hives.


Swelling similar to urticaria (hives), but the swelling occurs beneath the skin instead of on the surface. Angioedema is characterized by deep swelling that commonly occurs around the eyes and lips and sometimes of the hands and feet.


Specialized proteins produced by white blood cells that circulate in the blood. Antibodies seek and attach to foreign proteins, microorganisms or toxins in order to neutralize them. They are part of the immune system.


A substance, usually a protein, which the body perceives as foreign.


Medication that prevents symptoms of sneezing, itching, runny nose and possibly congestion by blocking



Conjunctivitis is an inflammation of the conjunctiva, the tissue that lines the inside of the eyelid. If the cause is bacterial infection, it is called "pink eye" or bacterial conjunctivitis. If the cause is allergic it is called allergic conjunctivitis.


Dander, animal

Tiny scales shed from animal skin and trap on animal fur or hair. Dander float in the air, settle on surfaces and make up much household dust. Cat dander are a classic cause of allergic reactions.


Medication that shrinks swollen nasal tissues to relieve symptoms of nasal swelling, congestion, and mucus secretion.


Inflammation of the skin, either due to direct contact with an irritating substance or to an allergic reaction.

Dust mites

A common trigger for indoor allergies. They are microscopic mites that live in the fibers of pillows, mattresses, blankets and carpet. They live off of our dead skin cells. Inhalation of their droppings can cause allergic reactions such as nasal congestion



High-efficiency particulate air (HEPA) filter that removes particles in the air by forcing it through screens containing microscopic pores.

Hay fever

Allergic reaction caused by the pollens of ragweed, grasses, trees and other plants whose pollen is spread by the wind.


A naturally occurring substance that is released by the immune system after being exposed to an allergen. When you inhale an allergen, mast cells located in the nose and sinus membranes release histamine. Histamine then attaches to receptors on nearby blood vessels, causing them to enlarge (dilate). Histamine also binds to other receptors located in nasal tissues, causing redness, swelling, itching and changes in the secretions.


See urticaria.


Products formulated to contain the fewest possible allergens.


Immune system

The body's defense system that protects us against infections and foreign substances.

Indoor allergies

A chronic disease characterized by an overreaction of the immune system to certain proteins found inside, such as mold spores, pet dander, cockroach or dust mite allergen, etc. (also called "perennial allergies")



Parasitic, microscopic fungi (like Alternaria) that float in the air like pollen. Mold is a common trigger for allergies and can be found in damp areas, such as the basement or bathroom, as well as in the outdoor environment in grass, leaf piles, hay, mulch or under mushrooms

Mold count

See pollen and mold count.


Outdoor allergies

A chronic disease characterized by an overreaction of the immune system to certain proteins found outside, such as tree, grass, or weed pollens, mold spores, stinging insects, plants, etc. (also called "hay fever," "nasal allergies," or "seasonal allergies").



A fine, powdery substance released by plants and trees.

Pollen and mold counts

A measure of the amount of allergens in the air. The counts are usually reported for mold spores and three types of pollen: grasses, trees and weeds. The count is reported as grains per cubic meter of air and is translated into a corresponding level: absent, low, medium or high.



An inflammation of the nasal passageways, particularly with discharge.



Inflammation of the sinuses caused by infectious (bacterial, viral or fungal) or non-infectious (allergic) inflammation. Acute bacterial sinusitis is diagnosed if a common cold does not resolve, but symptoms are less than 4 weeks. It can be treated with antibiotics and decongestants.


Urticaria (hives)

Itchy, swollen, red bumps or welts on the skin that appear suddenly. They may be a result of the body's adverse reaction to certain allergens. They can appear anywhere on the body including the face, lips, tongue, throat or ears.