Smartphones are fueling a dramatic rise in head lice among British schoolchildren, say scientists.
They cause kids to gather round in groups - allowing the itchy critters to jump from one child's locks to the next.
A study of more than 200 youngsters found those owning a smartphone - or tablet - were more than twice as likely to be infested with the tiny bugs.
Out of the 98 who did not have or use either type of device 29 experienced head lice - compared to 65 of the 104 (62.5%) who did.
The embarrassing social problem could be much more common than feared.
Almost half of the participants had been affected, up to 22 times more than the figure of two to eight percent that has been calculated in the past.
Taking regular selfies seemed to increased the risk but not by enough to conclude it was a factor, contrary to previous suggestions.
There is a theory that increasing use of portable devices such as smartphones and tablets has led to increased transmission of head lice.
Researcher Dr Tess McPherson, of Oxford University Hospitals NHS Foundation Trust, said: "Compared to previous estimates of head lice incidence our figures were much higher, showing that almost half of children have had them in the last five years, which may not come as a surprise to parents.
"We also noted that children with smartphones or tablets were more likely to get head lice, which is interesting but we can only guess that this is due to the way that young people gather around them, though there could be other reasons.
"Selfie culture gets its fair share of negative press so it's worth noting that despite previous speculation it seems that selfies can't specifically be blamed for helping the spread of head lice at this stage."
The study presented at the British Association of Dermatologists annual conference in Liverpool said previous estimates of the prevalence of head lice in British children "may be conservative".
It found 91 (45%) of the children had had head lice in the last five years, a longer period than covered by earlier research.
Girls with siblings aged six to nine were most commonly affected.
The study by Dr McPherson and colleagues found 82 (40.5%) of the children were using a device for selfies. It did not differentiate between individual and group selfies.
Matthew Gass, of the British Association of Dermatologists, said: "Head lice are a pain to deal with, both for children and their parents.
"Speaking from experience, they are intractable misery bugs that take far more time and effort to remove than is reasonable.
"Not to mention the obligatory quarantine period that they necessitate. That's why a better understanding of how these pests are transmitted is useful.
"Prevention is always better than a cure, particularly if the cure means wrenching your poor daughter's hair with a fine-toothed nit comb, or relying on over-the- counter remedies that head lice are increasingly resistant to.
"We're not saying that smartphones are causing children to get head lice, but that there is a link, so if there's an outbreak at home or at school, consider how electronic devices might cause children to congregate, allowing head lice to spread."
In the study questionnaires were given to parents or guardians attending the paediatric outpatient department at the John Radcliffe Hospital in Oxford, over a one-month period.
The survey collected information on sex, hair length, socioeconomic status and smartphone or tablet ownership.
Head lice live in hair and are particularly common in four to 11-year-olds - causing an itchy scalp and general discomfort.
They range in size from the size of a pinhead to that of a sesame seed and are a whitish or grey-brown colour.
A variety of treatments to get rid of head lice are available to buy from pharmacies, supermarkets, as well as online and you don't usually need to visit your GP to tackle the problem.
You catch them via direct head to head contact, where they climb from one person's hair to another's - they cannot jump, swim or fly.
They are very unlikely to be spread by items such as combs, hats or pillows and are specific to people - you can't catch them from animals.
Contrary to the old wives' tale, head lice have no preference for dirty or clean hair - nor short or long. They usually die within 12-24 hours of being removed from hair.