What temperature can lice withstand? - briefly
Adult head lice are killed by sustained exposure to temperatures of 50 °C (122 °F) or higher within a few minutes; they can endure brief exposure to near‑freezing temperatures but become inactive and do not survive prolonged cold.
What temperature can lice withstand? - in detail
Lice survive only within a narrow thermal range. Adult head‑lice (Pediculus humanus capitis) and their nymphs die rapidly when exposed to temperatures above 50 °C (122 °F) for more than a few minutes. Laboratory tests show 100 % mortality after 5 minutes at 55 °C (131 °F). Conversely, exposure to cold is equally lethal; temperatures at or below –5 °C (23 °F) cause irreversible damage within an hour, and freezing at –20 °C (‑4 °F) eliminates all stages within minutes.
The thermal limits differ slightly among life stages:
- Eggs (nits): Require higher heat to inactivate; 55 °C for 10 minutes guarantees hatch failure. Below 45 °C, eggs remain viable for several hours.
- Nymphs: Lose viability at 48 °C after 10 minutes; cooler thresholds are similar to adults.
- Adults: Fatal at 50 °C after 5 minutes; sub‑lethal exposure (40–45 °C) reduces mobility but does not kill.
Practical implications for eradication:
- Hot‑water laundering: Wash infested fabrics at ≥60 °C (140 °F) for at least 10 minutes; dryer heat of 70 °C (158 °F) for 20 minutes ensures complete kill.
- Cold‑temperature treatments: Freezing items for ≥24 hours at –20 °C (‑4 °F) reliably destroys all stages.
- Steam application: Steam generators delivering ≥100 °C (212 °F) for 5 seconds on hair or bedding achieve immediate mortality.
Any temperature exposure below these thresholds, whether heat or cold, may only suppress activity without guaranteeing elimination. Consistent application of the specified thermal parameters is essential for effective control.