Allergy to mold, dander, dust

Definition:

A collection of symptoms that occur after exposure to mold, animal dander, dust, or other substances in the environment that do not cause symptoms for most people (see also asthma; allergic rhinitis).

Causes, incidence, and risk factors:

Allergies are caused by hypersensitivity of the immune system, leading to a misdirected immune response. The immune system normally protects the body against harmful substances such as bacteria, viruses, and toxins. Allergy occurs when the immune system reacts to substances (allergens) that are generally harmless and in most people do not cause an immune response.

Allergy to environmental particles is a type of allergic rhinitis (hay fever). Hay fever usually involves an allergic reaction to pollen. However, people may develop an allergic reaction to other particles in the environment.

Many people are allergic to mold. Mold spores are carried in the air and may be present all year long. Mold is most prevalent indoors in damp locations and in swamp coolers, bathrooms, washrooms, fabrics, rugs, stuffed animals, books, wallpaper, and other "organic" materials. Outdoors, mold lives in the soil, on compost, and on damp vegetation.

Dust is another common allergen. House dust contains microscopic particles of pollen, mold, fibers from clothing and other fabrics, detergents, and microscopic insects (mites). Mites, including small fragments of dead mites, are the primary causes of dust allergy.

Many people are allergic to animals. Most people are not allergic to the animal's fur or feathers. They are actually allergic to the small scales of skin (dander) that the animal sheds. Some people are allergic to the animal's saliva, particularly cats (whose saliva contains a protein known to cause allergy). Saliva exposure occurs if the animal licks the person. It may also occur from petting the animal after it has groomed itself or by touching an object that the animal has recently licked or chewed.

A few people develop allergies to other irritants in the environment, including smoke, fumes from industries or cleaning products, tobacco, powder (face powder, baby powder, and so on.), laundry detergents, and other common substances.

When an allergen enters the body of a person with a sensitized immune system, it triggers antibody production. Histamine and other chemicals are released by body tissues as part of the immune response. This causes itching, swelling of affected tissues, mucus production, muscle spasms, hives and rashes, and other symptoms.

Symptoms vary in severity from person to person. Most environmental allergens contact the skin or are inhaled. Therefore, most symptoms affect the skin or the breathing passages.

Many disorders are associated with, triggered, or worsened by allergies. These include eczema, asthma, and many others.

Allergies are common. Heredity, environmental conditions, number and type of exposures, emotional factors (stress and emotional upset can increase the sensitivity of the immune system), and many other factors can indicate a predisposition to allergies.