Ask Tip Sheet

Are mildew and mold different things?

--RUTH ETZEL, ANCHORAGE, ALASKA

That depends on what you mean by "mildew." As a technical term, "mildew" refers to a type of crop disease. But for most people, "it's just slang for shower grunge," says environmental microbiologist Linda Stetzenbach. The nasty gray stuff in tile grout is usually a mixture of soap, skin cells, hair, yeast and--yep--some mold, a.k.a. fungi imperfecti. Unlike the toxic house-infesting mold blamed for ailments, shower grunge probably isn't dangerous to healthy people, since there's so little actual mold in it. Then again, Lysol isn't dangerous either, folks.