Scabies is an infestation caused by the microscopic mite Sarcoptes scabiei, which burrows into the outer layer of human skin to live and lay eggs. While medical treatment is necessary to eradicate mites on the body, the surrounding environment can harbor mites that lead to re-infestation. Controlling contamination on surfaces, clothing, and bedding is necessary to break the cycle of infestation and prevent recurrence after human treatment.
Mite Survival Time Off the Human Body
The timeline for environmental cleaning is determined by the short lifespan of the mite away from its human host. Under typical indoor conditions, scabies mites cannot survive for more than 48 to 72 hours off the human body. This survival window establishes the time frame for treating all potentially contaminated items.
Mite survival depends heavily on ambient temperature and relative humidity. Mites die quickly in high heat, but can survive longer in cooler, more humid environments. Mites have been reported to survive for more than a week in conditions cooler than 55°F (13°C) with high humidity. However, the 72-hour period is the standard guideline based on normal room temperatures, establishing the minimum isolation time for items that cannot be washed or dried.
Effective Chemical and Physical Agents
The most reliable methods for killing scabies mites on surfaces are agents that use heat or isolation, not chemical disinfectants. Standard antibacterial or antiviral surface cleaners are ineffective against the Sarcoptes scabiei mite. The most powerful agent against the mite and its eggs is high heat.
Heat treatments require temperatures above 122°F (50°C) for a sustained period to ensure mite mortality. Exposing the mites to this temperature for 10 to 20 minutes is sufficient to kill both the mites and their eggs. This principle is utilized through hot water washing, high-heat drying cycles, and steam cleaning.
Environmental sprays containing miticides or insecticides are available for surfaces that cannot be heated or isolated. These specialized products often contain pyrethrins or synthetic pyrethroids. They are designed to kill arthropods on non-living items like furniture, and are not for use on human skin.
Protocols for Washable Materials
All clothing, bedding, towels, and linens used by an infested person in the three days prior to treatment must be washed thoroughly. The washing machine cycle should be set to the hottest water temperature possible for the fabric, preferably above 122°F (50°C). Normal laundry detergents help physically remove the mites, but the high temperature is the component that kills them.
The drying process is important for ensuring mite death. Items should be placed in a mechanical dryer and run on the high-heat setting for a minimum of 20 minutes. For delicate items that cannot tolerate a hot wash cycle, use the high-heat dryer cycle alone or take them to a dry cleaner. If neither washing nor high-heat drying is possible, the materials must be isolated using the non-washable surface protocol.
Protocols for Non-Washable Surfaces
Non-washable items that have been in close contact with an infested person require alternative treatment. The most common method is isolation, which relies on the mite’s limited survival time off a host. Items such as mattresses, upholstered furniture, car seats, and stuffed toys must be sealed in a plastic bag for a minimum of 72 hours. Sealing them for a week is a safer measure to eliminate any mites that might survive longer in cooler conditions.
For upholstered furniture, rugs, and carpets, thorough vacuuming is necessary to physically remove mites and eggs from the fibers. The vacuum cleaner bag or canister contents must be immediately sealed in a plastic bag and disposed of outside the home. Steam cleaning is also an effective physical agent for mattresses and furniture, as the high temperature of the steam kills mites on contact. If an environmental insecticide spray is used, it should be applied strictly according to the manufacturer’s directions on the non-living surfaces.