Way back in the old days (in 1985) the FDA recommended voluntary limits on a carcinogenic by-product called 1,4-Dioxane that was commonly found in soaps and shampoos. That's more than 20 years ago that the dangers of the chemical were first widely known, yet today it is still found in the vast majority of our shampoos and bath products. This could be due the fact that the companies don't have to add it into the products for it to be there (it's formed as a by-product during the manufacturing process), and that there are no actual laws or tests required for monitoring levels (hence "voluntary limit").

Bad news: 18 out of 18 products tested contained some level of 1,4-Dioxane. Good news: most of the products tested were well below the recommended limit. Bad news: 1,4-Dioxane penetrates the skin. Good news: It evaporates quickly and most of the products it's found in are washed off quickly.

See the full article for some of the products that rated highest and lowest in 1,4-Dioxane levels.