How do lice die after treatment? - briefly
The active ingredients or heat in a lice remedy interfere with the insect’s nervous system or denature essential proteins, causing immediate paralysis and death within minutes to a few hours. The same action prevents viable hatching, so any remaining eggs either fail to develop or die shortly after treatment.
How do lice die after treatment? - in detail
Lice are eliminated after therapy through several distinct physiological disruptions caused by the applied agents.
Chemical pediculicides act primarily on the nervous system. Pyrethroids, such as permethrin, bind to voltage‑gated sodium channels, forcing them to remain open and producing uncontrolled nerve firing. The resulting paralysis halts respiration and leads to death within minutes to a few hours. Organophosphates like malathion inhibit acetylcholinesterase, causing accumulation of acetylcholine and continuous stimulation of muscles, which also ends in rapid paralysis. Carbamates (e.g., carbaryl) work by a similar enzyme‑inhibition mechanism, while spinosad targets nicotinic acetylcholine receptors, disrupting synaptic transmission.
Physical methods rely on environmental stress. High‑temperature treatments (e.g., steam or hair‑dryer heat at 50‑55 °C) denature proteins and destroy the cuticular lipids that maintain water balance, causing lethal dehydration in under ten minutes. Cryotherapy, using freezing sprays or cold‑air devices below –20 °C, forms ice crystals within the exoskeleton, rupturing cells and leading to immediate mortality.
Oil‑based products suffocate lice by coating the spiracles, the tiny breathing openings on the abdomen. The oil blocks gas exchange, induces hypoxia, and eventually causes death within several hours. The suffocating effect also loosens the cement that holds nits to hair shafts, facilitating removal.
The timeline of lethality varies with the mode of action. Neurotoxic chemicals typically kill adult lice within 30 minutes to 2 hours, whereas suffocants may require 4–8 hours. Physical heat or cold can achieve mortality in under 15 minutes if the temperature threshold is maintained consistently.
Eggs (nits) are resistant to most agents because their shells lack a functional nervous system and provide a barrier against chemicals and dehydration. Consequently, treatment protocols include a second application 7–10 days after the first, targeting newly hatched nits that have emerged from the protected stage.
Resistance development influences outcome. Mutations in sodium‑channel genes reduce pyrethroid binding, diminishing efficacy. In such cases, alternative classes (e.g., spinosad or malathion) or non‑chemical approaches become necessary.
Effective elimination therefore depends on selecting a method that disrupts a vital physiological process, applying it for the required exposure period, and repeating treatment to address surviving eggs.