How are lice expelled? - briefly
Lice leave the host by detaching naturally or after being killed by chemical or mechanical interventions, after which the bodies are discarded or washed away. Effective removal methods include fine‑tooth combing, approved topical insecticides, and laundering contaminated items in hot water.
How are lice expelled? - in detail
Lice are eliminated through several biological and therapeutic mechanisms that act on different stages of the parasite’s life cycle.
Mechanical removal targets adult insects and nymphs that reside on the host’s hair shafts. Regular combing with a fine‑toothed nit comb separates the insects from the strands, allowing them to fall to the ground. Repeated sessions, spaced 24–48 hours apart, ensure that newly hatched nymphs are captured before they mature.
Chemical agents interfere with the nervous system of the parasite. Pediculicides containing pyrethrins, permethrin, or dimethicone penetrate the cuticle, causing paralysis and death. Proper application follows product instructions regarding exposure time and repeat dosing, typically after 7–10 days to address any surviving eggs.
Environmental control reduces reinfestation sources. Washing bedding, clothing, and personal items in water above 50 °C for at least 10 minutes destroys both insects and eggs. Items that cannot be laundered may be sealed in plastic bags for two weeks, a period sufficient for hatching lice to die without a host.
Biological agents exploit natural predators of lice. Products based on entomopathogenic fungi, such as « Metarhizium anisopliae », infect the parasite, proliferating within its body and leading to mortality. These preparations are applied directly to the scalp and require several days to achieve full effect.
Thermal treatment employs high‑temperature devices that expose the hair and scalp to air or steam at 45–50 °C for a defined interval. The heat denatures proteins within the insect, resulting in rapid death. This method avoids chemical residues and is suitable for individuals with sensitivity to pediculicides.
Each approach addresses a specific vulnerability of the parasite: physical separation, neurotoxic disruption, environmental deprivation, microbial infection, or thermal injury. Combining methods—mechanical removal followed by a pediculicide and environmental sanitation—provides the highest probability of complete eradication.