What cannot lice tolerate? - briefly
Lice cannot survive extreme temperatures, sustained wet conditions, or direct contact with insecticidal chemicals.
What cannot lice tolerate? - in detail
Lice are highly sensitive to environmental and chemical factors that disrupt their physiology and reproductive cycle.
Temperature extremes prove lethal. Sustained exposure to temperatures above 130 °F (54 °C) or below 30 °F (−1 °C) destroys eggs and adult insects. Heat treatments that raise scalp temperature to 115 °F (46 °C) for 10 minutes effectively eradicate infestations.
Moisture imbalance also impairs survival. Dry conditions reduce humidity below 30 % relative humidity, causing desiccation of nymphs and adults. Conversely, excessive moisture creates an environment unsuitable for breathing through their spiracles, leading to drowning.
Chemical agents act as potent deterrents. Insecticides containing permethrin, pyrethrin, malathion, or spinosad interfere with neural transmission, resulting in paralysis and death. Non‑chemical substances such as dimethicone coat the exoskeleton, suffocating the parasite.
Physical disruption eliminates lice. Frequent combing with fine‑toothed lice combs removes eggs and adults from hair shafts. Repeated washing with hot water and detergent dislodges parasites and eliminates residual oils that attract them.
Nutritional deprivation limits reproduction. Absence of human blood meals for 24–48 hours halts egg laying, reducing population growth.
These factors—temperature extremes, humidity shifts, insecticidal compounds, suffocating agents, mechanical removal, and lack of nourishment—constitute the conditions lice cannot tolerate.