If one goes by a new study, not all YouTube tutorials can be trusted as two drunk friends, who went online to know how to increase manhood, were left with swollen penises after injecting piles cream.

In the Annals of Dermatology and Venereology journal, medics at Strasbourg University Hospital explained how the two French men, both in their thirties, landed in a hospital following the drunken experiment.

After taking advice from the video, the two decided to inject each other with anti-hematoma cream. But it didn't do them any good. 

Medics who treated the men said that during the night they had suffered swelling and visited the hospital the next day.

When they were examined, the patients said it hurt to touch their penises. They were prescribed painkillers by the doctors and were sent home, but it was not clear if they suffered any lasting damage.

Consultant urologist at the Queen Elizabeth Hospital in Birmingham, Dr Richard Viney, said you should never let anyone inject anything into your penis unless they are a qualified practitioner who can explain the risks involved and select the best option for you, reported The Sun.

The team in Strasbourg said this isn't a new trend. "Self-injection of various substances for the improvement of body shape, including increased penis size, was already described in texts, like the Kama Sutra more than 1500 years ago," they said.

"The size of their penis is a source of concern to some men and reconstructive penile surgery has become a relatively common practice. Some men receive penile injections that are performed by health-care practitioners or by non-medical practitioners, or in some cases by the individuals themselves."

The experts said that side effects like erectile dysfunction and even gangrene can occur in such cases.

Dr Viney told Daily Mail, "In this story we have two amateurs, under the influence of alcohol, injecting a product not designed to be injected in their penises under the guidance of a YouTube video. This was never going to work out well and there's a real likelihood that there will be irreversible damage with long term implications for their erections. This is something no right minded individual would do."

"Ultimately, the augmentation of the appearances of the genitals for both men and women carry with it risks of scarring and infection, poor results and a possible loss of function."

Ambulance Representational image. Photo by Mike Lawrie/Getty Images