Warnings about violence, etc. at plays

I just saw Jekyll and Hyde at our local Civic Light Opera, and there was a sign as we came in, warning that there would be flashing lights and gunshots in the production. However, the sign didn’t warn us about all the prostitution, murder (though that would be implied, to some extent, by the gunshot warning), blood, and singing, all of which could potentially offend or disgust some people.

I’d imagine that there is a lot of debate about what they “should” warn you about, as there is with movie ratings, parental advisory stickers, etc. But for plays, what are the theaters legally required to warn you about? What do they usually warn you about, so as not to anger their audiences, even though they aren’t required to? Have laws and general opinions on this changed over the years?

Flashing lights might be dangerous to epileptics; gunshots might be dangerous to someone with a bad heart, if they weren’t expecting it. It’s a health warning, not a “sensibilities” warning.

And now, ye may tear my post apart for the errors contained therein.