Once considered a minor ailment affecting only a few, asthma is now the most common chronic disorder in childhood, affecting an estimated 9 million American children under the age of 18.
And despite improvements in diagnosis and management, and a better understanding of the causes, the numbers have progressively increased over the past decades. In the United States alone, more than 8% of adults and 9% of children have been diagnosed with asthma, the Centers for Disease Control and Prevention reports.
An inflammatory disease, asthma can occur along the entire airway, from the nose to the lung. Once the airway becomes swollen and inflamed, it becomes narrower, and less air gets through to the lung tissue. This causes symptoms such as wheezing, coughing, chest tightness and trouble breathing.
During an asthma attack, the muscles around the airways tighten, and the asthma symptoms become worse than usual.
The fact that asthma runs in families suggests that genetic factors play an important role in the development of the disease. If one or both parents have asthma, the child is much more likely to develop the condition – this is known as genetic susceptibility. However, environmental factors also contribute to the disease process. Studies show that exposure to indoor allergens, from house dust mites, cockroaches, dogs, cats, rodents, molds and fungi, are among the most important asthma triggers.
Your Indoor Environment
From 1998-2002, researchers from the National Institute of Environmental Health Sciences and the Department of Housing and Urban Development conducted an extensive survey to assess the prevalence of these indoor allergens in American homes.
The results of this survey, known as the National Survey of Lead and Allergens in Housing, showed that more than 46% of homes have levels of dust mite allergens high enough to produce allergic reactions. Nearly a quarter have allergen levels high enough to trigger asthma symptoms in genetically susceptible individuals.
The survey also found that nearly two-thirds of American homes have detectable levels of cockroach allergens, with higher concentrations in high-rise apartments, urban settings, older homes and homes of low-income households. Approximately 10% of homes had cockroach allergen levels above the threshold for triggering asthma symptoms.
One of the most surprising findings from the national survey was that 100% of U.S. homes had detectable levels of dog and cat allergens, even though dogs were present in only 32% of the surveyed homes, and cat ownership was reported in only 24%. Most homes had levels of dog and cat allergens that exceeded the threshold for allergic sensitization, while about one-third of homes had allergen levels high enough to produce asthma symptoms.
Reducing Indoor Allergens
Beginning in the 1990s, scientists developed an intervention program that targets six major classes of allergens that trigger asthma symptoms – dust mites, cockroaches, pet dander, rodents, passive smoking and mold. Children who received the intervention had fewer unscheduled clinic visits, a reduction in the use of albuterol inhalers, and more symptom-free days over the course of the study than those in the control group. Here’s how you can reduce these allergens in your own home.
Dust mites
These tiny microscopic relatives of the spider live on mattresses, bedding, upholstered furniture, carpets and curtains.
They feed on the flakes of skin that people and pets shed daily and thrive in warm and humid environments. No matter how clean a home is, dust mites can’t be totally eliminated. But you can greatly reduce their numbers.
Preventive strategies:
- Use a dehumidifier or air conditioner to maintain relative humidity at about 50% or below.
- Encase your mattress and pillows in dustproof or allergen-impermeable covers (available from specialty supply mail-order companies, bedding stores and some department stores).
- Wash all bedding and blankets once a week in hot water (at least 130-140 degrees Farenheit) to kill dust mites. Non-washable bedding can be frozen overnight to kill dust mites.
- Replace wool or feathered bedding with synthetic materials and trade traditional stuffed animals with washable ones.
- If possible, replace wall-to-wall carpets in bedrooms with bare floors (linoleum, tile or wood) and remove fabric curtains and upholstered furniture.
- Use a damp mop or rag to remove dust. Never use a dry cloth, since this just stirs up mite allergens.
- Use a vacuum cleaner with either a double-layered microfilter bag or a HEPA filter to trap allergens that pass through a vacuum’s exhaust.
- Wear a mask while vacuuming to avoid inhaling allergens, and stay out of the vacuumed area for 20 minutes to allow any dust and allergens to settle.
Cockroaches
These are one of the most common and allergenic of indoor pests.
Recent studies have found a strong association between the presence of cockroaches and increases in the severity of asthma symptoms in individuals who are sensitive to their allergens.
These pests are common even in the cleanest of crowded urban areas and older dwellings. They’re found in all types of neighborhoods.
The proteins found in cockroach saliva are particularly allergenic, but the body and droppings of cockroaches also contain allergenic proteins.
Preventive strategies:
- Keep food and garbage in closed, tight-lidded containers. Never leave food out in the kitchen.
- Don’t leave out pet food or dirty food bowls. Eliminate water sources that attract these pests, such as leaky faucets and drain pipes.
- Mop the kitchen floor and wash countertops at least once a week.
- Plug up crevices around the house through which cockroaches can enter.
- Limit the spread of food around the house, especially in bedrooms.
- Use bait stations and other environmentally safe pesticides to reduce cockroach infestation.
Pets and animals
Many people think animal allergies are caused by the fur or feathers of their pet.
In fact, allergies are actually aggravated by the following:
- Proteins secreted by oil glands and shed as dander
- Proteins in saliva (which stick to fur when animals lick themselves)
- Aerosolized urine from rodents and guinea pigs
Keep in mind that even when animals are out of sight, their allergens aren’t. This is because pet allergens are carried on very small particles.
As a result, they circulate in the air and remain on carpets and furniture for weeks and months after a pet is gone.
Allergens may also be present in public buildings, schools and other places where there are no pets.
Preventive strategies:
- Remove pets from your home if possible.
- If pet removal isn’t possible, keep them out of bedrooms and confined to areas without carpets or upholstered furniture.
- Bathe pets weekly to reduce the amount of allergens.
- Wear a dust mask and gloves when near rodents.
- After playing with your pet, wash your hands and clean your clothes to remove allergens.
- Avoid contact with soiled litter cages
- Dust often with a damp cloth.
Mold
Several molds that grow both indoors and outdoors produce allergenic substances. These allergens can be found in mold spores and fungal structures such as hyphae, which anchor the mold and absorb nutrients.
Outdoor molds are seasonal, first appearing in early spring and thriving until the first frost. But there’s no definite seasonal pattern to molds that grow indoors.Indoor molds are found in dark, warm, humid and musty environments such as damp basements, cellars, attics, bathrooms and laundry rooms. They’re also found where fresh food is stored, as well as in refrigerator drip trays, garbage pails, air conditioners and humidifiers.
Outdoor molds grow in moist, shady areas. They’re common in soil, decaying vegetation, compost piles, rotting wood and fallen leaves.
Preventive strategies:
- Use a dehumidifier or air conditioner to maintain relative humidity below 50% and keep temperatures cool.
- Vent bathrooms and clothes dryers to the outside, and run bathroom and kitchen vents while bathing and cooking.
- Regularly check faucets, pipes and ductwork for leaks.
- When first turning on home or car air conditioners, leave the room or drive with the windows open for several minutes to allow mold spores to disperse.
- Remove decaying debris from the yard, roof and gutters.
- Avoid raking leaves, mowing lawns or working with peat, mulch, hay or dead wood. If you must do yardwork, wear a mask and avoid working on hot, humid days.
Adapted from “Asthma and Its Environmental Triggers” and “Allergens & Irritants” by the National Institute of Environmental Health Sciences, a division of the National Institutes of Health.
