While the chemicals in cosmetics make us look, feel, and smell better, research strongly suggests that at certain exposure levels, some of these chemicals may contribute to the development of cancer in people. But because personal care products contain a diverse combination of chemicals, it's nearly impossible to show a definite cause and effect for any specific chemical on its own.

Still, many of these chemicals are considered hormone disruptors. Hormone disruptors can affect how estrogen and other hormones act in the body, by blocking them or mimicking them, which throws off the body's hormonal balance. Because estrogen can make hormone-receptor-positive breast cancer develop and grow, many women choose to limit their exposure to these chemicals that can act like estrogen.

Most cosmetics and personal care products on store shelves today contain five major categories of toxic ingredients. These are: frank carcinogens (cancer causing); precursors of or “hidden” carcinogens; endocrine or hormonally disruptive; penetration enhancers; and allergens. Some toxic ingredients illegally remain unlabeled. Of particular concern are hormonal phthalates, and synthetic “aroma boosters” which strongly intensify organic fragrances.