Early exposure to indoor environmental factors, such as dust mites, molds, smoke, formaldehyde from building materials, and high levels of radon, can act directly by blocking a person's airways or indirectly by causing sensitivities to allergens.
By reducing exposure to air pollutants, the likelihood of developing allergies/sensitivities or suffering chronic allergic reactions can be reduced.
Environmental control can be especially helpful in preventing the development of asthma in infants.
The following suggestions can reduce a person's exposure to common household allergens by up to 95%: In the bedroom -

• Wash pillows, blankets, and other bedding monthly in hot water.
  
• Use foam pillows and enclose mattress and box spring in plastic mite-proof covers.
  
• Remove stuffed animals from beds.
  
• Remove bedroom carpeting or treat carpet with tannic acid, which denatures allergens.
  
• Eliminate exposure to pets or at least restrict your pets' access to the bedroom.
  

In the house -

• Keep windows closed, especially during "allergy season.
  "
• Avoid tobacco smoke.
  
• Achieve ideal relative humidity: use air conditioning and dehumidification to help reduce mold production if your home is too damp; if your home is too dry, use a humidifier.
  
• Use air filters (electrostatic precipitators and high-efficiency particulate air - HEPA) and purifiers (ionizers and ozone) to remove particulate matter and odors from the air.
  
• Use mite-specific exterminating chemicals, such as tannic acid, but be wary of commercial products.
  The Environmental Protection Agency recently pulled a dust mite product from the market.
  Although it was "allergist approved," it caused terrible reactions in people with allergies.
  Your best bet is to make your own tannic acid spray.