Indoor Allergens – Types and tips for controlling indoor allergens

Indoor Allergens


Any number of allergens present in an indoor environment such as the home or office can contribute to allergic reactions in sensitive people. These include dust mite droppings, mold, animal dander and cockroach debris. Most indoor allergens are made up of particles small enough that they can easily become airborne and inhaled. Individuals suffering from asthma find that many types of indoor allergens can irritate their airways and cause an asthma attack.

There are a variety of techniques that can be used to control the amount of indoor allergens in the home or office. While it is impossible to remove every type of indoor allergen from an environment, using a HEPA filter or a dehumidifier can help reduce the amount of allergens present. Other techniques are also available to reduce the amount of specific allergens (e.g., mold, dust mites, dander).

Tobacco smoke and smoke from wood-burning stoves can also aggravate respiratory problems when encountered indoors. Individuals should try to limit their exposure to these substances.

Many allergens cannot be completely removed from an indoor environment. Therefore, patients may require allergy medications to help treat their symptoms. In addition, allergy shots (immunotherapy) are sometimes effective at treating individuals who suffer from sensitivity to indoor allergens.

About indoor allergens

Considering the amount of time most people spend in their home and at work, it is very important that these environments be kept relatively free of allergens. People suffering from airborne allergies or asthma are often plagued by the presence of these substances.

The most common types of indoor allergens include:

  • Dust and dust mites
  • Animal dander
  • Cockroach debris
  • Mold

Because of their tiny size, indoor allergens can easily become airborne. While many types of indoor allergens settle onto surfaces when the air is still, they are often stirred up into the air once disturbed. This can occur when a person is cleaning, opening a door or simply walking through a room. Once allergens are in the air they are easily inhaled. Oftentimes, airborne allergens are spread throughout the house via an air conditioning system.

Indoor allergens include a type of protein that triggers an allergic reaction when inhaled by a sensitive individual. The protein is mistakenly perceived as a threat by the immune system, which responds by releasing chemicals into the blood. These chemicals cause allergy symptoms including runny nose, coughing, sneezing, itchy eyes and nasal congestion.

People with allergies that trigger asthma-like symptoms, or those who have allergic asthma, can have an asthma attack after inhaling an indoor allergen. Airborne allergens can disturb or irritate the sensitive muscles in an asthmatic person’s airways, causing those muscles to constrict. This can lead to shortness of breath or difficulty breathing.

In order to determine if a patient is sensitive to indoor allergens, a physician will conduct a physical examination and compile the patient’s medical history, including a list of symptoms. In addition, an allergy skin test or blood test may be performed.

While indoor allergens are not usually seasonal like many types of outdoor allergens, late summer usually sees higher levels of dust mites (due to higher humidity), molds and some pollens (which can be tracked indoors or brought in on clothes).

These circumstances can cause some people to experience more severe indoor allergy symptoms in summer. However, cold temperatures in the winter are often responsible for keeping people shut inside for long periods of time. This has the effect of both increasing the amount of exposure an individual has to indoor allergens, and raising the amount of allergens in the home due to the decreased ventilation. Most houses are closed tight during winter.

Research also suggests that indoor allergen levels vary throughout the United States. A recent study found that people in the Northeast and areas of the Midwest had the highest exposure and sensitivity levels to cockroach debris. Dust mite allergens, on the other hand, were most prominent in the South and Northwest.

Some buildings have ongoing indoor air quality problems as a result of poor building design or occupant activities. This is called sick building syndrome (SBS). Chemical contaminants, inadequate ventilation and biological contaminants (e.g., molds, pollens) are factors that are commonly associated with SBS. People who suffer from indoor allergies may find their condition aggravated if living or working in a building with SBS.

Types and differences of indoor allergens

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.

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.

Tips for controlling indoor allergens

There are several things an individual can do to control the amount of allergens found in the home. While many allergens can never be completely removed from the home, there are many ways to limit the amount present.

Controlling home allergens is the most effective method of managing indoor allergies. Some general tips include:

  • Use a true HEPA filter or HEPA vacuum cleaner. These filters are capable of removing all types of airborne allergens from the air (air filter) or a surface (vacuum cleaner).

  • Replace air filters and clean vents frequently.

  • Use only hardwood or tile floors, or use washable rugs. Allergens can more easily accumulate on carpeting.

  • Use shades instead of blinds or draperies on windows. Fewer allergens build up on shades, and they are easier to clean.

  • Use furniture covered in leather or vinyl. Allergens can more easily accumulate on cloth or fabric upholstery.

  • Keep humidity down. Use a dehumidifier or air conditioning to control humidity levels in the home. Mold grows much more rapidly when the humidity level is greater than 50 percent. Cockroaches favor humid environments, as well.

Depending on an individual’s particular type of allergy, there are several specific steps that can be taken to limit allergens. Since most common indoor allergens can be components of house dust, controlling dust will also help control these allergens. Tips for controlling dust include:

  • Keep surfaces free of clutter.

  • Using special hypoallergenic covers for the mattress, box spring and pillows can limit the amount of dust mites found in the bed.

  • Opening the windows every day for an hour can help remove dust mites and indoor molds, especially in winter. However, this should only be done when high levels of outdoor molds or pollens are not present.

  • Wash bedding every two weeks in water of at least 140 degrees Fahrenheit (60 degrees Celsius). Throw rugs should also be washed regularly in hot water or dry cleaned.

  • Remove stuffed animals, books and other dust-collecting items from the bedroom.

  • Vacuum at least once or twice a week (preferably with a HEPA vacuum cleaner). Individuals with dust allergies should wear a mask while vacuuming and performing other cleaning activities, and leave the house for several hours after cleaning. This can help patients avoid exposure to disturbed dust.

Additional tips for controlling cockroach debris include:

  • Keep all food in sealed containers.

  • Promptly clean dirty dishes as well as any food spills, cooking surfaces and crumbs.

  • Use an insecticide anywhere roaches may frequent, or consider a professional exterminator.

  • Avoid eating in bed.

Additional tips for controlling animal dander include:

  • Limit the amount of time pets are allowed to spend in commonly used rooms, and keep the bedroom strictly pet-free.

  • Use an antiallergenic shampoo on pets and bathe them at least once a week. Allow someone else to bathe the pet if allergies are severe.

  • Wash hands after handling the pet.

  • Provide pets with a well-balanced diet; minimizing fur loss may reduce indoor dander.

  • Place litter boxes away from any air filtration vents.

Additional tips for controlling mold and mildew include:

  • Check for hidden molds anywhere water is commonly allowed to stand (e.g., plant containers, windowsills).

  • Use mildew-resistant shower curtains.

  • Fix any leaky faucets or pipes.

  • Use exhaust fans in any areas where humidity tends to be high (e.g., bathroom, kitchen).

  • Frequently clean the refrigerator’s drip pan or use a frost-free refrigerator.

Although these steps can help patients reduce their contact with indoor allergens, exposure can still occur. Therefore, allergy medications may be needed to help control symptoms. A number of prescription and over-the-counter medications may be recommended, including antihistamines, decongestants and corticosteroids.

If medication treatment fails to relieve symptoms, a physician may recommend allergy shots  (immunotherapy). This type of therapy works by regularly exposing an individual to very small amounts of an allergen through a series of injections. By increasing their exposure to the allergen over a period of months or years, some individuals are able to build up a tolerance to the allergen. While not a cure, allergy shots can lessen the severity and frequency of allergic reactions in some people. The success of this type of treatment varies by individual.

Questions for your doctor

Preparing questions in advance can help patients to have more meaningful discussions with their physicians. Patients may wish to ask their doctors the following questions about indoor allergens:

  1. Do my symptoms suggest indoor allergies?

  2. What tests will you use to determine if I suffer from indoor allergies?

  3. What may be causing my indoor allergies?

  4. What are my treatment options?

  5. What steps can I take to reduce the amount of indoor allergens in my home?

  6. What steps can I take to reduce the amount of indoor allergens in my office?

  7. Will my symptoms be consistent or vary based on the time of year?

  8. Are my children likely to have indoor allergies as well?

  9. Would I benefit from the use of a HEPA filter?

  10. Would I benefit from the use of a dehumidifier?
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