Nothing wrong with natural beauty, but if she is in certain industries it's more professional to at least have some coverup and mascara on. Some people need just a little touch to look out together. If she is in fashion or an exec in business it's pretty standard to expect people to look their best. Of course, OP could be a male named Sarah in which case we should all be ashamed for assuming OP is a woman:)

Tell him to go **** himself.

Isn't that kind of harassment? I would talk to somebody in HR, confidentially at first, to see what are your options. Unless, of course, your job description and thus performance are related to occupation in world of beauty and wearing appropriate clothing and make up.

What a ****.

That sucks, it's people like this that continue to hold society back from progression.

Any time someone suggests I wear makeup, I always reply "You first", since more often than not, the one suggesting it isn't wearing makeup themselves, or they are male. It tends to shut them off (Or just make them even more pissy with me, which is just as good) Makeup is ******* expensive, and if you've spent basically all your life not wearing it, you're going to waste a lot of it learning how to properly apply it to where it's not overwhelming, and it's even. Not to mention dealing with resisting the urge to rub your face because you feel something foreign on it.

Don't let it get to you, you know like that song “you are beautiful in every single way, words can't bring us down”

Tell your boss he needs to eat makeup so he can be pretty on the inside.

See, I'm the type of person who likes to bitch back and say, "At least I'm not fat." But don't do that. Only to those who you would lock in your basement.

What in the hell of hells? As others suggested, whether this is FYL or YDI does somewhat depend on context. If you're selling clinique products in a fancy store/wherever, there probably is a general expectation you wear makeup (for instance). If you're shelving books in a library, not so much (for instance). Ultimately though, hell with him. I don't wear makeup, and there's no way I'd be forced into doing so. Take it up with HR if he persists.