How long do lice live in water? - briefly
Lice survive only a few minutes in water, typically dying within 5–10 minutes, and they cannot remain alive beyond an hour. Their aquatic tolerance is extremely low, leading to rapid mortality.
How long do lice live in water? - in detail
Lice are obligate ectoparasites that require a host’s blood for nourishment. When they are placed in water, respiration through spiracles ceases and the insects quickly become incapable of feeding. Survival time varies with species, temperature, and water quality.
- Head lice (Pediculus humanus capitis): typically survive 10–20 minutes in fresh water at room temperature (20‑25 °C). Cooler water (below 15 °C) can extend viability to about 30 minutes, while warm water (above 30 °C) reduces survival to less than 5 minutes.
- Body lice (Pediculus humanus humanus): show similar limits, lasting roughly 15 minutes in tap water at 22 °C. Saline solutions shorten survival to under 10 minutes because osmotic stress accelerates dehydration.
- Pubic lice (Pthirus pubis): tend to persist slightly longer, up to 30 minutes in stagnant water, but high‑temperature baths (≥40 °C) kill them within 5 minutes.
Key factors influencing duration:
- Temperature: Higher temperatures increase metabolic rate and hasten loss of respiratory function; lower temperatures slow metabolism, marginally prolonging life.
- Osmolarity: Pure water causes rapid swelling of the insect’s cuticle, leading to rupture; hyper‑tonic solutions draw fluids out, causing dehydration.
- Water movement: Turbulent flow can dislodge lice from the surface, exposing spiracles to water and causing immediate drowning.
- Age and health of the insect: Nymphs, with thinner exoskeletons, succumb faster than mature adults.
Laboratory tests confirm that after 30 minutes of immersion, virtually no viable lice remain, regardless of species. Consequently, rinsing hair or clothing with water does not constitute an effective eradication method; chemical or mechanical removal is required for reliable control.