At what temperature do lice die? - briefly
Lice are eliminated when exposed to temperatures of 50 °C (122 °F) or higher for several minutes; at 60 °C (140 °F) they die within seconds.
At what temperature do lice die? - in detail
Lice are eliminated when exposed to temperatures that disrupt protein structures and cellular membranes. Laboratory experiments show that a sustained temperature of 54 °C (130 °F) kills adult head lice within five minutes. Temperatures of 48–50 °C (118–122 °F) cause mortality in 10–15 minutes, while 45 °C (113 °F) requires 30 minutes or longer for complete kill rates. The eggs (nits) are more resistant; they survive 45 °C for at least 30 minutes but are destroyed at 55 °C (131 °F) within five minutes.
Practical heat‑based eradication methods rely on these thresholds:
- Washing clothing, bedding, and hats at 60 °C (140 °F) for at least 10 minutes.
- Drying items on high heat for a minimum of 30 minutes; dryer temperatures typically exceed 70 °C (158 °F).
- Applying a handheld steamer that produces steam above 100 °C (212 °F) to hair and scalp for 10 minutes, ensuring steam penetrates the hair shaft.
- Using a professional heat‑treatment device that maintains 55 °C (131 °F) for 10 minutes across the entire scalp area.
Cold exposure also leads to mortality, but only after prolonged periods. Freezing at –20 °C (–4 °F) for 24 hours can kill both lice and nits, yet this method is impractical for personal use.
The effectiveness of heat treatment depends on maintaining the target temperature uniformly and for the specified duration. Inconsistent heating allows some insects to survive, especially the more resilient eggs. Therefore, protocols that combine washing, high‑heat drying, and direct steam application provide the most reliable eradication.