The Japanese site Naver Matome recently identified a fad in which middle schoolers lick one another’s eye balls. The act has led to an outbreak of pink eye, discovered after teachers noticed growing numbers of students wearing eye patches to school. One teacher described the moment he first witnessed students engaging in the act, considered the equivalent of reaching second base among their peer group.

“After class one day, I went into the equipment store in the gymnasium to tidy up. The door had been left open, and when I looked inside, a male pupil and a female pupil had their faces close together and were kind of fumbling around,” Mr. Y explained, according to Japan Crush’s English translation. “Could it be bullying? I wondered, but when I had a good look, the boy was licking the girl’s eye! Surprised, a shouted ‘What are you doing? Stop it at once!’ and the two of them were so shocked they jumped apart. The girl burst into tears, and the boy just went bright red and was shaken up.”

After questioning the students, Mr. Y learned that the students were “dating” and licking one another’s eyeballs was the considered next step after French kissing. When he advised school staff, and assembly was held where teachers found 30 percent of sixth graders at the school had participated in eyeball licking. The students were unaware that the activity promoted the spread of trachoma, the bacteria that cause both conjunctivitis (pink eye) and chlamydia.

Shanghailist.com offered one possible inspiration for the fad: the lead singer of the Japanese band Born allows his eyeball to be licked in a music video—by a knife-wielding woman, no less.

Although the trend was recently identified, evidence suggests the practice of eyeball licking has been out there for awhile. A 2008 thread on Reddit asks users if they find eyeball licking “weird or cool?” Readers responded with answers such as “(My) high-school girlfriend was into it… the fact that it weirds people out makes me like it even more,” and “My wife does it to me, I have returned the favor occasionally.”

Another Reddit user recalled that one of the questions on the classic Web site TheSpark.com—which featured a variety of personality tests and off-the-wall science experiments before Barnes & Noble purchased and shut it down in 2005—purity test pertained to eyeball licking. “Have you ever licked someone’s eyeball or had yours licked?” was, in fact, question No. 92 on Spark’s purity test, just after a question about sex with a stranger and preceding another regarding Golden Showers.

When Spark readers took the test a decade ago, most were likely appalled at the question or simply laughed it off. Now we know there were actually some people who must have answered, “yes.”