Salmon sperm to bird droppings: The science behind bizarre skincare rituals - BBC

At the You & I Clinic in Seoul, South Korea, one of the most requested skin texture treatments involves injecting tiny fragments of DNA from salmon sperm into the dermis, the skin's thick middle layer which houses the blood vessels, nerves and glands.

"The goal is not volume, like a filler, but skin priming or biostimulation, which involves supporting a healthier dermal environment and recovery," says Kyu‑Ho Yi, an aesthetic physician at the clinic and an adjunct professor at Yonsei University.

The idea might seem bizarre, but Yi says the concept actually originates from the world of regenerative medicine and wound healing, where DNA fragments from fish gained attention for their potential to stimulate tissue repair in people with facial scars from combat injuries.

Scientific data remains relatively sparse, but some studies suggest that the treatments – which harness the salmon sperm's purified polynucleotides – may help reduce the appearance of fine lines.

They've been shown "to help improve skin hydration, plumpness, texture and wrinkles", says Joshua Zeichner, associate professor of dermatology at Mount Sinai Hospital, in the US, who has also worked for skincare companies as a consultant. "It's unclear how someone first decided to try this as a skin treatment, but nonetheless, it's being used."

With South Korea now viewed as a trendsetter in aesthetics – otherwise dubbed as the K-Beauty craze – the supposed benefits of salmon and other fish sperm injections have spread around the globe, encouraged by a flurry of celebrities ranging from Charli XCX to Jennifer Aniston. Their popularity has risen alongside a collection of other odd-sounding treatments, which include facemasks made of bird droppings and blood-sucking vampire facials.

But do these unusual, trendy skincare regimens actually work?

A quick glance through the history books shows that skincare has a long and storied history of seemingly odd practices. The Egyptian queen Cleopatra is rumoured to have bathed in sour donkey milk. In Myanmar, women have applied a paste known as thanaka to their faces for centuries, made from ground tree bark, both as a decorative practice, and to shield their skin from sun damage. One notorious Roman remedy for blemishes involved grinding up the guts of a small crocodile.

Yet modern skin science suggests that at least a few of these ancient beauty therapies have stood the test of time, with ingredients like turmeric, tiger grass and seaweed popping up in modern-day products thanks to their anti-inflammatory and skin-hydrating effects.

In 2022, a study examined various skincare practices from 12th-Century Italy that had been cited in the writings of a famed female medieval medical practitioner called Trota of Salerno. The researchers noted that many of the suggested ingredients, such as fava beans and vinegar, are now considered to be effective for facial cleansing, exfoliating, and treating dry skin. An extract of tartar oil called tartaric acid, for instance, is now a common ingredient in modern skincare.

Geisha facials and menstrual masking

It's not just plants, herbs and minerals found in nature. The so-called "Geisha Facial" involves taking excrement from nightingale birds, sanitising it using powerful ultraviolet light, mixing it with other chemicals such as an exfoliant and a brightener, before applying it like a face mask. This coprocentric technique originates from a centuries-old Japanese discovery that the droppings of Japanese bush warblers, a type of nightingale, could be used as a dye remover in fabrics. This then led to the droppings being used by Japanese female entertainers for skin whitening and removing their heavy makeup.

Nowadays, it's popular in various clinics around the world as a way of brightening the skin, and again, there could be some sound science behind it. According to Zeichner, nightingales leave particularly high concentrations of urea in their droppings, a chemical with such potent skin softening qualities that it's commonly incorporated into moisturisers.

It also contains high concentrations of the amino acid guanine. "Amino acids have been shown to have hydrating and brightening benefits," says Zeichner. "But it's important to say that these [treatments] use purified, modified nightingale droppings. You shouldn't just scoop up bird poop off the street and rub that onto your face."