There are a variety of airborne allergens responsible for triggering allergies inside the home and workplace. These include:

• House dust. Mixture that contains tiny particles of soil, plant material, human and animal skin, hair, fabric fibers and insect parts. It is often one of these specific components that is responsible for triggering an allergy. These particles can easily become airborne and inhaled when disturbed. House dust is considered the most common type of indoor allergen. This is in part because all the other common indoor allergens can be components of house dust.
  
  
• Dust mite droppings. Dust mites are microscopic arachnids (related to spiders) not visible to the naked eye. They usually live deep within carpeting, upholstery and mattresses, where they feed on shed epithelial (skin) cells. It is not the dust mites themselves that are allergens, it is the digestive enzymes found in their droppings. Dust mite droppings usually disintegrate from a pellet into a fine powder, which can easily be stirred up into the air and inhaled. Dust mites are the most common type of allergic trigger for individuals with asthma.
  
  
• Dander. Tiny flakes of skin shed from animals – usually pets (e.g., dogs, cats, birds). The proteins are secreted by oil glands in the animal’s skin. Since animals are constantly shedding dander, allergens are deposited around any area in which the animal is present. In contained areas, such as a home, the accumulation of these substances is more likely to become airborne and trigger an allergic reaction in people with animal allergies.
  
  
• Cockroach debris. Small particles of cockroach droppings, saliva, eggs and outer coverings. These particles contain a protein that can trigger an allergic reaction in some people when inhaled. Cockroach debris is often a component of household dust, which can become airborne if disturbed, and then inhaled. Cockroaches are attracted to food sources and household food wastes, and favor damp areas. Many homes in the United States have cockroaches living in them, even if they are never seen.
  
  
• Mold and mildew. Mold spores are airborne particles found in damp indoor areas such as bathrooms and basements. The term mildew usually refers to mold that can be seen. As mold grows, it releases mold spores into the air. Airborne mold can be directly inhaled or settle into household dust. Mold can be invisible to the naked eye and grow unseen behind walls and under floor tiles.
  
  

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Though many people assume that indoor houseplants are off-limits to anyone with a strong allergic reaction to pollen, few indoor plants are actually problematic. This is because indoor plants generally do not flower or pollinate as much as outdoor plants. However, two types of common houseplant – the weeping fig and flowering maple – can cause eye allergies and trigger asthma, respectively. People allergic to mold should reduce the number of potted plants in the home because soil is an ideal place for mold to grow.

Tobacco smoke is one of the most commonly acknowledged asthma triggers. It can also complicate allergic conditions because of its effects on the respiratory system. Both direct smoking and inhaling secondhand smoke are harmful. Secondhand smoke can cause the most damage to others in close, indoor areas.

Individuals with allergies should also be aware of the danger from smoke generated from wood-burning stoves. While this type of smoke is not itself an allergen, studies have demonstrated that wood smoke can cause an increase in respiratory symptoms, lowered respiratory function and lowered pulmonary function. Smoke is also a common irritant of asthmatics. Asthma sufferers should try to stay away from wood-burning stoves and fireplaces.