Experts are issuing an urgent warning to men - stop rubbing toothpaste on your penis to last longer in bed.
The bizarre trend has sprung up following a number of YouTube videos claiming it can help men "Get Hard Erection" and "Increase Timing".
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One video, which has racked up over 1 million views, states the dubious advantages of applying toothpaste.
"In toothpaste is more than you can clean your teeth, sex has become more hard and make an erection more lasting effects," the voice-over says.
Men are advised to "massage toothpaste on the tip of your penis" in order to "crush premature ejaculation and erectile dysfunction".
But medical experts are warning this could have dire and unwanted effects, including burns, blisters and scarring.
Consultant pharmacist James O'Loan warns the peppermint oils and chemicals in toothpaste - which include bleaching agents - can be "extremely irritating" to sensitive skin.
"I'd urge anyone thinking of trying this rather worrying 'toothpaste' technique to cease and desist," he told the Daily Mail.
"It won't do anything at all to combat premature ejaculation or erectile dysfunction, despite the claims being made in these videos.
"By putting it on your genitals, you actually risk a mild burn, as well as blisters and scarring. And toothpaste should in no way be used as a lubricant, either."
Urologist Rich Viney told the Daily Mail the "abrasive" properties of toothpaste make sex uncomfortable.
"It could lead to infections in the woman's vagina. You do not want foreign material inside the vagina, it's an irritant," he said.
"Anyone using toothpaste for sex is kidding themselves. There's real remedies that work out there."