​Our shower steamer recipe doesn't use citric acid. Citric acid will cause a fizzing reaction, which is actually unnecessary because you don't need fizz to come up from the floor of the shower. However, if you're more of a bath person than a shower person, so you wanted to use this recipe to make bath bombs rather than shower steamers, you'd want to add citric acid because the fizzy reaction is part of the appeal of bath bombs.