You're making your way across a dimly lit parking lot, a single flickering streetlamp showing you the way. You suddenly become aware that, despite the late hour, you aren't alone. Someone else is heading out, too, presumably to a car parked near yours.
But then everything takes a turn -- you're being mugged.
You quickly reach into your bag to try to find something you can defend yourself with and feel a can of pepper spray at your fingertips. You whip it out and squirt it at your would-be assailant. Microseconds later he drops to the ground and begins clawing at his face, for all the world looking like he doesn't want his eyeballs to remain lodged in his eye sockets.
This doesn't surprise you at all. Pepper spray causes eye irritation ... that's what it's for! But take a look at the can: "May irritate eyes." Apparently, at some point, that just wasn't clear.