Many of us don't realize that we spend about one-third of each day at home (except less for workaholics) and during this time we are exposed to potential indoor allergens.

The most common causes of indoor or year-round allergies include house dust, dust mites, pet dander, feather bedding, mold spores and cockroach allergens. During the wintertime, indoor air is rather dry and we may feel it with parched, chapped lips and dry skin. Many people prefer to use an indoor humidifier to moisturize the air for greater comfort as well as to soothe dry nasal and sinus passages.

The number one indoor allergen for most people with allergies is the "house dust mite" (a potent indoor allergen within dust). These spider-like critters (fortunately you cannot see them without a microscope) love to inhabit warm, cozy places like pillows, mattresses, box springs and duvet covers in the bedroom. You may have as many as two million dust mites in your bedding! So what do they need to survive? Moisture! As we moisturize the indoor air with a humidifier, we are actually mobilizing them for a real party as they absorb water from the nearby environment.

If you happen to use a humidifier, it is essential to monitor the level of indoor humidity with a hygrometer (costs about $10-15). You want to avoid over doing it and keep the level of humidity indoors below 50 percent (shoot for range of 30-50percent). Follow the manufacturer's instructions for cleaning a humidifier and refill with fresh water daily.

Get some more expert advice from the American Academy of Allergy, Asthma and Immunology at_ http://www.aaaai.org/patients/topicofthemonth/1107/ and http://www.aaaai.org/winterallergy/2006/.

Check out the American College of Allergy, Asthma and Immunology's website at: http://www.acaai.org/public/indoor/indoor.htm.

Dr. Clifford W. Bassett is an assistant clinical professor of medicine at the Long Island College Hospital and on the faculty of NYU School of Medicine. He is the current vice chair for public education committee of the American Academy of Allergy, Asthma and Immunology. No information in this blog is intended as medical advice to any reader or intended to diagnose or treat any medical condition.