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Women and men who regularly trim or remove all their pubic hair run a greater risk of sexually transmitted infections (STIs) than those who do not, research suggests.

Doctors say small tears in the skin from shaving or trimming could make it easier for infections to take hold.

But they also say groomers - particularly extreme ones - tend to be more sexually active too.

STIs are passed on through unprotected sex or genital contact.

The findings come from a survey of more than 7,500 American adults, published in Sexually Transmitted Infections - a specialist BMJ journal.

The report, led by doctors from the University of California, San Francisco, said the two most likely explanations for the link between grooming and STIs were micro-tears in the skin, which increased the risk of viral STIs, and groomers being more likely to engage in risky sexual behaviour with more sexual partners.

Extreme cut

An electric razor was the most common tool used for pubic grooming among men, while a manual razor was more common among women.

About one in five men and women used scissors.

The researchers said it was unlikely that sharing grooming tools was an issue, because traces of the most common STIs had not been found on objects before.

But they did say doctors should advise groomers to cut back a little on their grooming or put off having sex until the skin had healed completely.

Almost three-quarters of respondents said they had groomed their pubic hair before, with 84% of women and 66% of men saying they had trimmed, shaved or waxed in the past.

Among the groomers, 17% described themselves as "extreme" - removing all hair at least once a month - and 22% as "high frequency" - trimming daily or weekly.

Lice protection

In the survey, any type of grooming was linked to an increased risk of having a sexually transmitted infection. And the more frequent and extreme the grooming, the greater the risk.

Those with the most extreme habits were three to four times more likely to contract an STI, particularly infections from skin to skin contact such as herpes and HPV (human papillomavirus).

But there was good news for groomers too - because their habit was found to protect against pubic lice.

The report said: "If grooming is found to protect against lice, individuals at risk for pubic lice could be counselled to remove their pubic hair."

What are STIs?

Examples are gonnorhea, herpes, syphilis and genital warts

The most common STI is chlamydia, which is easily passed on during sex

Young heterosexuals under 25 and men who have sex with men are most affected by STIs

Most sexually transmitted infections can be treated, and it is best if treatment starts as soon as possible

How to reduce the risk?