However, the expense and the risks are unnecessary as a safe and effective non-chemical method of beth treatment and prevention is available. A pesticide loses its effectiveness when the lice become resistant to it. But there is nothing to stop chemists from selling treatments not on the current rotation. Some treatments are not effective because the instructions are difficult to follow. Lotions must be left on about 10 hours and must cover the hair completely.
Shampoos can be over-diluted or washed off before they have had time to act.
Neither work unless repeated. Exposure Exposure to the pesticides in headlice treatments is significantly higher than from eating food containing pesticide residues. Pesticides are toxic compounds and while they may well cause no hazard at the very low levels detected on food, frequent treatment can increase exposure to levels where there is a risk. Even if not high enough to cause any health risks to the individuals treated, the amount of pesticides washed down the drain to pollute water is of real concern to wildlife. Health hazards All of the pesticides used against headlice are toxic at high levels and there is concern about frequent exposure to lower levels.