What Is It? Quaternium-15 might sound like something out of a sci-fi fantasy flick, but this toxic ingredient is definitely the real deal. Technically an ammonium salt, quaternium-15 is used as a preservative in many skin and hair products, including, but not limited to, makeup, facial cleanser, self-tanner, shampoo, conditioner and many personal care products meant specifically for babies.

Health Risk: Our biggest concern? Yes, quaternium-15 commonly causes allergic reactions and dermatitis. And yes, it irritates your skin, your eyes, and your respiratory system. But quaternium-15 breaks down into formaldehyde: a known carcinogen. With so many toxins floating around in our world already, there is no way we want to get this potentially cancer-causing chemical anywhere near our noggins.

How To Avoid It: Scour the personal-care shelves for quaternium-15-free options! For the little ones, we turn to The Honest Company or California Baby’s toxin-free line of skin, hair, bath and sun care. And for the young-at-heart? We adore Dr. Alkaitis’s organic hair-care line (as well as their facial-care products) to keep us glowing, inside and out!