Penny is perturbed: I’ve been using Aveeno Baby Sunblock Lotion on my 2 year old but I read that it contains dioxane which causes cancer. Should I switch sunscreens? The Left Brain explains:

What is dioxane?

Penny, the chemical you’re referring to is actually 1,4-dioxane. It’s not an ingredient so it won’t be listed on the package, but it is a contaminant that does show up in small amounts in some cosmetic raw materials. Typically it comes from ingredients that have “PEG,” or “Polyethylene” in the name. In the case of the Aveno sunscreen it comes from PEG-100 stearate, which is used to dissolve the oil soluble ingredients in the product.

Can this chemical be dangerous?

Yes, under some conditions. 1,4 dioxane was linked to cancer in animal feeding studies done in the 1970s by the National Cancer Institute. Given that danger, the FDA decided to conduct additional studies to determine if the chemical can penetrate skin when applied from cosmetics. They found that yes it can. But they also found out that since the levels of 1,4 dioxane in cosmetics are low and that since it evaporates relatively quickly, very little actually gets into the skin. So this appears to be another case of an ingredient that is carcinogenic at very high levels but does not pose a danger under normal use conditions.

Is my sunblock safe?

Yes, according to the FDA: “The 1,4-dioxane levels we have seen in our monitoring of cosmetics do not present a hazard to consumers.” Furthermore, they say that their testing shows that levels of 1,4 dioxane are actually decreasing due to improved manufacturing processes. For more details, including full technical references, see the FDA’s report on 1,4 dioxane. That’s good enough for me.