A dehumidifier removes moisture and keeps the humidity at appropriate levels. Without one, the surrounding air feels uncomfortably damp and sticky. Humidity makes it hard for the body to regulate its internal temperature, so you may feel hot and sweat more. Besides discomfort, humid air encourages allergens, dust mites, and other particulate matter to linger in the household. These contaminants damage the lungs and worsen pre-existing conditions. The best dehumidifiers will remove moisture from the air to protect occupants with allergies, asthma, or other pulmonary diseases. Removing moisture is critical to prevent damage when humidity is too high. Dehumidifiers don't have to run all the time either: most of the best dehumidifiers automatically shut off when the desired humidity level is reached. Then, they test the air to see how much moisture is present and run accordingly.