Head lice are tiny parasitic insects that inhabit the human scalp, feeding on small amounts of blood. They are a common nuisance, particularly among school-aged children, causing itching and discomfort. Understanding how temperature affects these pests is an important aspect of managing and controlling an infestation.
Lethal Temperatures for Lice
Head lice are highly susceptible to high temperatures. Live lice are killed when exposed to temperatures at or above 130°F (54.4°C) for at least five minutes.
Lice eggs, known as nits, are more resilient than adult lice but also succumb to sustained heat. Nits require exposure to temperatures of 130°F (54.4°C) for a minimum of five to ten minutes. Common household appliances like hot water washing machines and clothes dryers can reach these temperatures, making them useful tools for decontamination.
Lice and Cold Temperatures
While lice thrive in the warm environment of the human scalp, extreme cold can also be lethal. Lice and nits die when exposed to sustained freezing temperatures. Research indicates that temperatures below 5°F (-15°C) for at least 48 hours are effective.
Temperatures of 0°F (-18°C) or lower can kill lice within a few hours. However, cold is generally less effective for eradication compared to heat, as typical household freezers might not consistently reach the necessary low temperatures.
Applying Temperature Control for Eradication
Utilizing temperature control is a practical way to manage lice infestations on items rather than on the scalp. Bedding, clothing, and other washable items should be machine washed using hot water. The water temperature should be at least 130°F (54.4°C) to kill both lice and nits.
After washing, these items should be tumble-dried on a high heat setting for a minimum of 40 minutes. The dryer’s heat, typically ranging from 135°F to 150°F (57.2°C to 65.6°C), is sufficient to kill any remaining lice or eggs. Even non-washable items like stuffed animals or pillows can be placed directly into a hot dryer for a full cycle.
For non-washable items that cannot be subjected to high heat, sealing them in a plastic bag for two weeks is an alternative method. This duration is sufficient to starve any lice, as they cannot survive long off a human host. Alternatively, these items can be placed in a freezer at 0°F (-18°C) or lower for several hours or days to kill lice and nits. Vacuuming carpets and furniture can help remove any lice or nits that may have fallen off the host.