Definition of Allergy to mold - animal dander - dust:

Allergy-related symptoms can occur after you are around mold, certain animals or animal hair, dust, and other substances. These substances are usually found indoors and do not cause symptoms for most people.

See also:

• Asthma
• Allergic rhinitis

Causes, incidence, and risk factors:

Allergies occurs when the immune system over-reacts to substances (allergens) that are usually harmless.

When a person with allergies breathes in an allergen, the body releases histamine and other chemicals as part of the immune response. This causes itching and swelling, mucus production, and in serious cases, hives and rashes, as well as other symptoms. Symptoms vary in severity from person to person.

Click here to see a video about hives.

Most environmental allergens contact the skin or eyes, or are inhaled. Therefore, most symptoms affect the skin, eyes, or the breathing passages.

You may develop an allergic reaction to particles that may be in or outdoors. Common allergy triggers include:

• Mold -- Mold spores are carried in the air and may be present all year long. Mold is most common indoors in damp locations such as basements, bathrooms, or washrooms. Fabrics, rugs, stuffed animals, books, or wallpaper can contain mold spores if they are kept in a damp place. Outdoors, mold lives in the soil, on compost, and on damp vegetation.
• Animals -- People who are allergic to certain animals are rarely allergic to the animals' 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. Cats have saliva that contains a protein known to cause allergy. You can come into contact with animal saliva if the pet licks you, if you touched the pet after it has groomed itself, or if you touch an object that the animal has recently licked or chewed. Similar reactions can occur with dog saliva exposure.
• Dust -- House dust contains tiny particles of pollen, mold, fibers from clothing and fabrics, detergents, and microscopic insects (mites). Dust mites, including small fragments of dead mites, are the primary cause of dust allergy and are found in the highest numbers in bedding, mattresses, and box springs.

A few people develop allergy-like symptoms to other irritants in the environment, including smoke, fumes from industries or cleaning products, tobacco, powder, and laundry detergents.