selfie
Models pull faces as they take a selfie before presenting Carmen Marc Valvo 2014 Autumn/Winter collectionReuters

Thanks to stars including Kim Kardashian, Miley Cyrus and even Barack Obama the 'selfie' has become a global phenomenon.

Social media favourites such as Instagram, Facebook and Twitter are now laden with image of teens and celebrities pouting away for self-snapped camera shots at every opportunity and at any venue.

But now a health expert has warned that huddling up with mates for a 'selfie' is causing a rise in the incidence of head lice. 

Marcy McQuillian, who runs two Nitless Noggins treatment centrers in Los Gatos and Scotts Valley, in the US, claims that head bumping for group selfies has contributed to the rise in the number of young people in the US, especially teenage girls, contracting headlice.

"Typically its younger children I treat, because they are at a higher risk of head-to-head contact," she told San Francisco news website sfist.com.

"But now, teens are sticking their heads together to take mobile phone pictures. Every teen I've treated, I ask about selfies and they admit they are taking them every day."

She added that "parents need to be aware and teenagers need to be aware too. Selfies are fun but the consequences are real".

While  a number of experts said it was possible, some dermatologists insist that selfies are not responsible for the surge in nits and branded McQuillian's theory as nothing but a PR stunt.

Dr Richard Pollack from the Harvard School of Health told NBC News: "This is a marketing ploy, pure and simple. Where these louse salons open a branch, there always seems to be some kind of epidemic."

Headlice are blood-sucking insects that are spread through direct head-to-head contact with an infested person. Sharing combs, headwear or bedding can also aid transmission.