Parabens are groups of chemicals used as preservatives in a wide variety of beauty products (up to 90 percent of them, from shampoo to toothpaste to self-tanner) and sometimes as food additives. Some parabens are found in nature, like the antimicrobal fruit of the blueberry shrub, but all commercial types are synthetic.
Despite many years of seemingly safe use, studies have begun to suggest that the use of parabens is less than healthy. One of the most famous studies linked the use of parabens in antiperspirants to breast cancer after researchers found parabens in samples of breast tumors. According to the American Cancer Society, there is "no good scientific evidence to support this claim" and "ongoing studies to date have not shown any direct link between parabens and breast cancer risk" — but the organization does acknowledge the need for further scientific investigation. Many companies have released paraben-free products that are worth a try while the jury's out.