Periods! If they didn't exist, literally none of us would exist either. And yet, they still seem to make some people uncomfortable and grossed out—yes, even some ADULT humans (generally of the male persuasion, not that we're pointing fingers).
Here's one story about a guy who got so uncomfortable about a co-worker's period, he actually reported her to H.R. This story, originally shared on Mumsnet by user "Snuffalo," will make your period blood boil (if that grosses you out, don't read ahead, and also you should probably leave society).
Snuffalo writes that she was suffering from "horrible menstrual cramps" and painkillers weren't helping (BEEN THERE), so she was holding a hot water bottle in her lap.
Here's what happened next:
My sort-of-supervisor* we’ll call Guy comes over to talk to me about something, notices the hot water bottle, says “there’s no way you’re cold today, are you?” I say “um, no, just for the pain relief”. He looks confused and then literally horrified and then he walks away.