How does copper sulfate solution act on lice and nits? - briefly
Copper sulfate solution kills lice and prevents nits from hatching by disrupting neural function and damaging the egg shell. Its biocidal action results from copper ions penetrating the cuticle and denaturing essential proteins.
How does copper sulfate solution act on lice and nits? - in detail
Copper sulfate solution kills adult lice and prevents egg hatching through several biochemical actions. Copper ions penetrate the insect cuticle and bind to sulfhydryl groups in enzymes, disrupting respiration and energy metabolism. This inhibition leads to rapid paralysis and death of the parasite. In addition, copper ions cause oxidative damage to cellular membranes, increasing permeability and resulting in loss of essential ions and water.
When applied to eggs, the solution penetrates the porous chorion, denatures proteins required for embryonic development, and interferes with the activity of chitin synthase, preventing proper shell formation. Exposure for 10–15 minutes at concentrations of 5–10 % (w/v) is sufficient to achieve >90 % mortality of nymphs and to halt hatching of viable eggs.
Key factors influencing efficacy:
- Concentration: Solutions below 2 % show limited activity; optimal results reported at 5–10 % copper sulfate.
- Contact time: Minimum 10 minutes required for adult lethality; 20 minutes recommended for complete ovicidal effect.
- Temperature: Higher ambient temperatures (20–25 °C) enhance penetration and enzymatic disruption.
- pH: Slightly acidic formulations (pH 5–6) improve copper ion solubility and bioavailability.
Safety considerations include dermal irritation and potential staining of hair and skin. Protective gloves and thorough rinsing after treatment reduce adverse effects. Copper accumulation in the environment warrants careful disposal of excess solution; it should not be poured into wastewater without neutralization.
Resistance development is unlikely because copper targets multiple metabolic pathways simultaneously, unlike single‑mode neurotoxic agents. However, repeated sub‑lethal exposure may select for tolerant populations, emphasizing the need for correct dosing and adherence to recommended exposure periods.
In practice, the solution is applied to dry hair, massaged into the scalp, left for the prescribed duration, then rinsed thoroughly. Follow‑up treatment after 7–10 days eliminates any newly emerged lice from eggs that survived the initial application.