What do lice dislike on the head? - briefly
Lice are repelled by oily scalp conditions and substances such as tea‑tree oil, neem oil, high‑concentration alcohol, or other essential oils. They also avoid environments with elevated temperature or frequent washing that removes their feeding substrate.
What do lice dislike on the head? - in detail
Lice are highly sensitive to several physical and chemical conditions on the scalp. Their survival depends on a stable, warm, and moist environment; any deviation can deter them.
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High concentrations of ethanol or isopropyl alcohol: quickly desiccate the exoskeleton and disrupt respiratory spiracles. Direct application of products containing at least 70 % alcohol creates an inhospitable surface.
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Essential oils with proven acaricidal activity: tea tree (Melaleuca alternifolia), peppermint (Mentha × piperita), and eucalyptus (Eucalyptus globulus) contain terpenes that interfere with neural signaling in lice. Concentrations of 2–5 % in carrier oils are effective without harming skin.
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Low pH environments: acidic shampoos (pH 4.5–5.0) impair the cuticle’s integrity. Acidic formulations destabilize the protective wax layer, leading to dehydration.
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High temperature: exposure to 54 °C (130 °F) for 5 minutes denatures proteins and kills both nymphs and adults. Heat‑based devices exploit this threshold.
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Silicone‑based polymers: dimethicone creates a coating that blocks the insect’s ability to grip hair shafts, causing loss of mobility and eventual death. Concentrations of 1–2 % are sufficient.
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Heavy mineral oil: forms a physical barrier that suffocates lice by occluding spiracles. Application of 5 ml per scalp area for 10 minutes suffices.
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Frequent washing with surfactant‑rich shampoos: removes the lipid layer that lice rely on for adhesion. Surfactants such as sodium lauryl sulfate disrupt the cuticular lipids.
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Dry scalp conditions: reduced moisture lowers the humidity around the hair, making the environment unsuitable for lice metabolism.
Combining these deterrents—chemical (alcohol, essential oils, acidic agents), physical (heat, silicone polymers), and environmental (dryness, frequent cleansing)—maximizes the likelihood of repelling or eliminating head‑dwelling lice.