My MIL never cleans house. Usually when we stay there we find a way to send her to the store so I can scrub out part of the kitchen, her bathroom or vacuum at least. She just doesn't care. I've been doing this for 13 years. I've never said anything, I sure don't want to hurt her feelings EVER - she's one of the most wonderful people I've ever known.

I'd just... travel with cleaning supplies. I find they really do come in handy. I'm also pretty sensitive to mold. Sorry you had that experience, that would have been really freaky. But i wouldn't tell your friend about it.