Guest Author - Amy Anaruk

Allergen - substance causing an allergic reaction. An allergen is an antigen that, in non-allergic people, doesn't invoke the immune response.

Allergy - excessive immune response to an antigen, or foreign substance, not normally harmful to the body. Allergic symptoms can manifest themselves in the nose (rhinitis), the lungs (asthma), the skin (eczema, uriatica), and the digestive system.

Anaphylaxis - life-threatening, whole-body allergic reaction. An individual in anaphylactic shock will experience sudden, severe release of histamine from tissues throughout the body, leading to serious airway restriction, pulmonary edemas, and heart arrhythmias. This type of reaction can cause death within minutes or even seconds, so patients with anaphylactic allergies must carry emergency medication at all times. Research suggests having asthma increases the risk of anaphylaxis in patients with food allergies.

Antibody - immune protein, or immunoglobulin, that normally works to protect the body against foreign substances. An allergic person produces antibodies in response to typically benign substances.

Antigen - foreign substance that causes the body to mount a defensive immune response. A virus is an example of an antigen. When a virus enters the body of a healthy person, the immune system produces an antibody to bind to the antigen, helping to neutralize and destroy it to make that person healthy again. People with allergies have immune systems that recognize non-harmful substances--pollen, for example--as antigens.

Antihistamines - drugs that block histamine to reduce the allergic reaction.

Contact Dermatitis (CD) - skin rash or inflammation that occurs after a person comes in contact with a certain substance. CD can occur with no allergies present when actual skin damage occurs. Strong chemical cleaners, for example, can irritate the skin and cause CD with no involvement of the immune system.

Eczema - allergic condition of the skin featuring inflamed patches that can itch, crust, scale, and blister. Also called atopic dermatitis, meaning an allergy-related case of dermatitis that does not require contact to produce the inflammation. Eczema sufferers often also suffer from rhinitis and/or asthma. Eczema, rhinitis, and asthma tend to run in families.

Extrinsic asthma - asthma with allergy-related triggers. Patients who experience flares after breathing in allergens like dust or mold have extrinsic asthma. Also called allergic asthma. Most children have this type of asthma.

Hay Fever - pollen-triggered rhinitis that occurs in the fall and spring.

Histamine - naturally occurring chemical that helps produce the inflammatory immune response. Allergic people produce too much histamine during times when their bodies don't need it. Histamine reactions can involve runny noses, watery and itchy eyes, asthma flares, skin rashes, and (with food allergies) digestive problems.

Immunoglobulin E (IgE) - the antibody responsible for allergic reactions. People with allergies have elevated levels of IgE in their blood.

Immunotherapy - allergy shots, a preventative method of treating allergies. During immunotherapy, an allergist administers a long-term regimen of shots that contain incrementally higher doses of the specific substances that cause allergic reactions in the patient. Over time, the shots desensitize the patient's immune system to those allergens.

Intrinsic asthma - asthma with non-allergic triggers. A person with intrinsic asthma might experience flares during respiratory infections or after breathing in smoke or dust. Intrinsic asthma is harder to treat than allergic asthma and is more common in adults than children.

Rhinitis - allergic response of the nasal passages that produces runny and stuffy noses, itching, and sneezing. Technically, rhinitis refers to inflammation of the nasal mucus membrane and occurs when an allergic person inhales an allergen like pollen.

Urticaria - the clinical term for hives, or raised itchy welts on the skin. Usually, but not always, caused by allergens. Hives are usually temporary, lasting up to a few weeks, but in some rare cases can be severe and chronic. Food allergies often cause hives.