Almost all head lice are now immune to over-the-counter treatments - meaning parents will find it more difficult than ever to keep their children nit free.A new study has found that 98 per cent of head lice can't be killed by pyrethrins and permethrins, the chemicals used in many anti-nit treatments.The report's authors say if over-the-counter treatments fail to clear up head lice parents may need to ask their doctor for prescription treatments.Lead author Dr Chris Belcher said: "It's...
