Once a month, a 33-year-old Irish man would fill a syringe with his own semen and squirt it into the veins and muscles of his right arm, hoping it would make his chronic lower back pain go away.

Sorry, we don't understand it either. It's a new one for the books.

Physicians came across this unusual case when its subject admitted himself into a Dublin hospital following several days of lower back pain brought on by lifting a heavy object.

Following an examination, medical staff discovered his lower right arm was red and slightly swollen, with signs of a fairly serious subcutaneous infection. An X-ray revealed signs of an abscess deep under the skin.

The patient disclosed it was most likely caused by recent injections of his own semen. Apparently back pain was an ongoing problem for the gentleman, and he'd come up with a rather innovative plan to treat it by introducing his own ejaculate intravenously and intramuscularly.

For the previous year and a half he'd been giving himself a monthly shot of his own self-made tonic. In the wake of his most recent bout of back pain, he had even upped his dose to several injections.

The case study was outlined in an Irish Medical Journal article back in January 2019, playfully titled "Semenly" Harmless Back Pain: An Unusual Presentation of a Subcutaneous Abscess. Its authors dug into the literature – both clinical and alternative – for some kind of explanation, but came up empty handed.

"A comprehensive review of EMBASE, PubMed, Google scholar and the wider internet was conducted with an emphasis on intravenous semen injection for the treatment of back pain as well as for other medical and non-medical uses," the authors wrote.

"Although there is a report of the effects of subcutaneous semen injection into rats and rabbits [in 1945], there were no cases of intravenous semen injection into humans found across the literature."

Alleged health benefits of semen have been debated in the literature. It's occasionally injected just under the skin in minuscule amounts to test for allergic reactions, and has been contested as a way to treat semen-sensitivities.

But when it comes to reducing pain, let alone specifically treating back injuries, this is pretty much unheard of.

No doubt there's more to this man's story. Not that we'll get to the bottom of it any time soon, and possibly doctors won't, either.

The patient was diagnosed with cellulitis - a bacterial infection of the skin - and the doctors gave him intravenous antimicrobial drugs; but before they could administer further treatment, he discharged himself.

Apparently, his back felt better.

This research was published in the Irish Medical Journal.

A version of this article was first published in January 2019.