boric acid in eyedrops

[mikan]

Not long ago I was looking at over-the-counter eyedrops at the drug store, and I was surprised to find that Visine and other similar products contain boric acid. Having previously encountered boric acid only as a white powder that kills cockroaches like nothing else, I decided that I might not want to be putting the stuff in my eyes. Anyone out there got a good explanation for why boric acid is in common eyedrops? Would it be harmful if used frequently?

[smilingjaws]

Boric acid is recommended first aid for washing out your eyes. It must be similar to eye fluids.

[torq]

The Merck Index doesn't list "eye drops" as a common use of boric acid, but it does say that it's an antiseptic; my guess is that that's the reason it's in there.

As for being a cockroach poison... sure, but consider how much you put out for them, and how big they are compared to you. Toxic human doses are from "less than 5 grams" for infants up to "5 to 20 grams" for adults (again from the Merck).