Mention respiratory allergies and asthma and most people think of the outdoors. The bad news is the allergens that affect most people are actually indoors and cause problems year-round. The good news is people allergic to indoor allergens can often control them.

Dr. James Meyer, a pulmonologist who treats allergy and asthma patients in Iowa, says in addition to obtaining treatment, patients should keep floors and other surfaces clean and dust-free, capture as many airborne particles as possible and control the relative humidity of the home.

Cleaning with a built-in central vacuum system has been clinically proven to reduce allergy symptoms by as much as 60 percent.

"A central vacuum system gives the homeowner maximum cleaning power, completely removes contacted dust and allergens from the living area and doesn't stir up dust in the home," says Larry Hartley, marketing director for Electrolux Home Care Products, maker of Beam Central Vacuum Systems. The systems also offer a wide variety of tools and accessories to clean both carpeted and hard-surface floors, blinds, upholstery, ceiling fans, fireplaces and even the garage.

Fewer airborne allergens resulting from using a central vacuum will help air filtration systems work more effectively. Meyer and other physicians recommend patients install pleated filters with a rating of MERV 12 or greater in forced air heating and cooling systems.

Maintaining the home's relative humidity at 50 percent or lower will slow the growth of dust mite populations, thereby limiting patients' exposure.

Patients should also keep their physicians informed of any changes in their home environment or symptoms.