Cockroaches and dust mites spike their droppings with a highly allergenic protein. Cockroach sensitivity and exposure are common among patients with asthma who live in inner cities. In an inner-city asthma study, asthma severity increased with increasing levels of cockroach antigen in the bedrooms of sensitized children. Humidifiers and evaporative coolers are potentially harmful because increased humidity may encourage the growth of both mold and house-dust mites. In addition, humidifiers may pose a problem if not properly cleaned because they can harbor and aerosolize mold spores.
Air conditioning allows windows and doors to stay closed, which prevents entry of outside allergens.
Regular use of central air conditioning also will usually control humidity sufficiently to reduce house-dust mite growth. These patients also should stay out of rooms where a vacuum cleaner is being or has just been used. Air cleaners cannot significantly reduce exposure to house-dust mite and cockroach allergens because these heavy particles do not remain airborne.