Avoid parabens. Synthetic preservatives that disrupt hormones and may stimulate cancerous tumors, parabens are found in most commercial sunscreens, as well as hundreds of other products like antiperspirant, shampoo, and face wash. The most common types – methylparaben, propylparaben, and butylparaben – usually appear last on ingredient lists, so a quick scan can tell you whether to pass on a product. Also avoid vitamin A, sometimes called retinyl palmitate, because it breaks down into toxic free radicals when exposed to UV, causing skin to age and increasing cancer risk.