Eyeball Licking: What If…

This summer, Western media leapt upon a post on Japanese curation site Naver Matome which detailed a sudden increase in the practice of oculolinctus. Oculolinctus, or “worming”, is the niche activity of eyeball-licking. The story has since been exposed as a hoax, deliciously playing on the love of certain sections of the media for bizarre news.

However, the exposure given to the topic makes an outbreak of oculolinctus, considered by some to be a sexual fetish, more likely. How damaging could the practice be to the eye?

Undiluted, sterile saliva is toxic to corneal epithelial cells. This is not, as is often proposed, attributable to amylase action; rather, it is due to the hypotonicity of the saliva (isotonic saliva is not toxic). But the data comes from prolonged exposure of cultured corneal epithelial cells. In intact eyes, blinking renders the interaction with undiluted saliva brief, and unlikely to be damaging.

Saliva microflora differ between individuals, reflecting diet and hygiene. It could be speculated that oculolinctus presents a high load of bacteria or viruses to the eye and, especially if it is introduced from a diseased mouth or other body part, could lead to conjunctivitis or styes.

The antimicrobial defence of the tear film is adept at dealing with the usual introduction of microorganisms: a little saliva seems not to pose a threat, as evidenced by the number of people that habitually lick their contact lenses to no ill effect. But extended exposure via oculolinctus does, theoretically, raise one issue. Tear lipocalin (TLC) is a major component of the tear film and is involved in regulation of tear viscosity, binding and release of lipids, endonuclease inactivation of viral DNA, binding of microbial siderophores. It also has anti-inflammatory activity. Introducing other mucosal fluids, that contain no or little TLC, may alter its concentration sufficient to impede its role. 

Further concerns? Debris in the saliva or extensive licking could scratch the cornea. Indeed, David Granet of the Shiley Eye Center in San Diego, CA, told The Huffington Post that “There are ridges on the tongue that can cause a corneal abrasion. And if a person hasn’t washed out their mouth, they might put acid from citrus products or spices into the eye.”

Forewarned is forearmed. If ever there is an “EYEBALL LICKING craze that’s sweeping Japan and causing a surge in eye infections” (1), we now know what to expect.