Allergic rhinitis: A medical term for allergy symptoms including sneezing, congestion, runny nose, red or watery eyes, and itchiness in the nose, throat, eyes, and ears. It's sometimes called hay fever.

Allergist: A doctor who specializes in treating people suffering from allergies. Pediatric allergists specialize in treating children.

Antacids: Common medicines that are taken to relieve the symptoms of acid indigestion. Antacids may be liquid or tablets, prescription or nonprescription.

Antibody: A molecule in the body that reacts with a specific substance that caused it to be formed. People with allergies produce large amounts of antibodies to the particular allergens they're allergic to.

Antibiotics: A class of drugs used to combat infection due to bacteria. (See bacteria.)

Antifungal: A class of medicines used to combat fungal infection. (See fungus.)

Antihistamine: A medication that blocks the action of histamine. ZYRTEC is an antihistamine.

Bacteria (plural of bacterium): A general name for a large class of single-celled organisms. Some bacteria cause disease, and some are useful, such as the bacteria that are used to produce some drugs and treat sewage.

Bacterial: Relating to or caused by bacteria. (See Bacteria.)

Birch: Type of tree or shrub that flowers and releases pollens from January – February in the South and from April – May in the Northeast and Midwest.

Corticosteroids: Corticosteroids inhibit the body's inflammation process, thereby decreasing nasal congestion and the secretion of nasal mucus. Corticosteroids are sprayed directly into the nose to relieve sneezing, nasal itching, congestion, and runny nose.

Decongestants: A class of medicines that reduce congestion or swelling. Nasal decongestants can reduce stuffiness to make breathing easier.

Duck: The feathers from ducks and other birds release the dander that causes allergies. Feathers in pillows, comforters, and cushions can produce an allergic reaction.

Dust: A general name for tiny airborne particles, that may include bits of plants, dust mites, insect material, dirt, fiber, animal dander, or other household material.

Dust mites: Microscopic insects that are commonly found in household dust. They are the frequent cause of dust allergies.

Electrostatic precipitator: A system in some air cleaners that uses a weak electric charge to attract tiny allergen particles, thus removing them from the air.

Elm: A type of tree that sheds its leaves in the fall. Elm trees release pollens in February in the South and from March – April in the Northern part of the country.

FDA (Food & Drug Administration): The governmental agency responsible for evaluating and regulating the safety and effectiveness of prescription drugs.

Feathers: (See Duck, Goose down.)

Fungal: Of, resembling, or characteristic of a fungus which is a class of microscopic plants that reproduce via tiny spores. (See Fungus.)

Fungus (plural of fungi): A class of microscopic plants that reproduce via tiny spores. Fungi may be used in the production of foods such as cheese or soy sauce. They can cause allergic reactions in sensitive people, and occasionally infections.

Goose down: The fine, soft feathers of a goose. If you’re allergic to feathers, you’re most likely also allergic to goose down.

Grass: The primary grasses that cause allergies are Timothy, Blue (or June), Sweet Vernal, and Bermuda. Grasses primarily release pollens during the late spring and summer months, except for Bermuda grass which releases pollens in the South year-round.

Histamine: An inflammatory substance produced by the body that is responsible for causing allergy symptoms in some people.

Hives (urticaria): A skin allergy that produces swelling, redness, and itching.

Immune system: The medical term for the mechanism that protects the body from foreign substances like disease-causing bacteria or viruses.

Immunotherapy: A method of reducing the long-term immune response to allergens, in which small amounts of the allergy-causing substance is injected for a period of time.

Indoor (perennial) allergies: The allergic reactions produced by indoor allergens such as dust, mold, and pet dander.

Mold: A fungus that grows in hot spots such as damp basements, closets, bathrooms. The seeds of molds are called spores. Each spore that germinates creates new mold growth.

Nasal Congestion: More commonly called stuffy nose. Nasal congestion is an inflammation of the mucous membranes of the nose that can make breathing difficult.

Oak: Any of a number of a variety of trees or shrubs that bear acorns as fruits. Oaks produce abundant pollen and are a major cause of allergies.

Outdoor (seasonal) allergies: The allergic reactions produced by molds, and pollens from trees, grass, and weeds.

Pet dander: The name for the dried skin flakes, urine, and saliva from cats, dogs, and other animals that cause allergies.

Pollen: The powdery reproductive material released into the air by male flowering plants. Pollen from trees, grass, and weeds is a common cause of allergies.

Pollen count: A standard scale that measures how likely you are to experience allergy symptoms if you are allergic to tree, grass, or weed pollen, and certain molds. You can use the pollen count to help manage your allergy symptoms.

Proteins: Complex molecules involved in the allergic response. It is the proteins in pet dander that cause allergic reaction.

Rabbit: The saliva, skin, and urine of pets contain proteins. When these flake or dry, they drift into the air; that’s the pet dander that causes your allergies.

Ragweed: A weed with yellow flowers. Responsible for the longest and most severe pollen seasons in the East and Midwest.

Spores: The very small "seeds" released by mold and fungi.

Viral: Relating to or caused by a virus. (See Virus.)

Virus: A class of disease-causing particles that are resistant to antibiotics and antifungals. Influenza ("the flu") and the common cold are caused by viruses.

Weeds: Pigweed, Goosefoot, Ragweed, and Sagebrush are the primary groups of weeds that release the pollens that cause allergies.

Wheezing: Breathing with difficulty, which often sounds dry, raspy, and produces a whistling sound.