Research has revealed that head lice have become resistant to the active ingredients in most over the counter remedies available in pharmacies.

Normally, head lice are treated with insecticides, specifically pyrethrins and permethrins, and a fine tooth comb, to scrape out the dead lice and eggs.

A US study, published in the Journal of Economic Entomology, has revealed that 98% of head lice have developed a resistance to these insecticides.

Chemical head lice treatments usually don’t kill all of the head lice, so the survivors can develop an immunity to the insecticide.

The researchers, who are based at the Peyton Manning Children's Hospital in Indianapolis, urged parents of children with head lice to ask their doctor for alternative treatments to tackle nits.

"This newly published data supports what we've been seeing in our offices and clinics: an increase in treatment-resistant super lice," said the study's lead author Dr Chris Belcher.

"It's important that parents contact a clinician if they suspect their child has head lice.

"There are effective, non-pyrethrin, non-pyrethroid-based prescription agents that can be used if treatment with over-the-counter products such as Nix has been unsuccessful."

The report reveals that lice’s gene have mutated partially due people overusing over-the-counter medications as treatment.

Head lice are small, wingless parasitic insects that live on human heads, drawing blood from the scalp and clinging to hair.