You’ve been stalking nail art for months on Pinterest, and you tried unsuccessfully to give yourself a Katy Perry-inspired manicure. And then find yourself in the nail polish aisle of a drugstore, debating which hue looks best.

But before you pick out that perfect shade, know that about half of the nail polishes in the Environmental Working Group’s database contain a chemical that could be toxic. The chemical is called triphenyl (try- fen-el) phosphate, or TPP for short. It’s used in some nail polishes and manicuring products to increase their flexibility and durability, and it can also help the polish stick to your nails. Typically, TPP is used to make products like furniture cushions less flammable.

TPP in nail polish could seep through the wearer’s nails over time, according to a recent study by the Environmental Working Group and Duke University. This study doesn’t necessarily prove that TPP is toxic to humans, but it does show that chemicals can come into our bodies through fingernails.

In the past, scientists who studied TPP’s effects found that mice that were exposed to the chemical for about a month had shrunken testes. In another study, rats that were exposed to a fire retardant mixture containing TPP were obese, and females went through early puberty. Human men are also affected by TPP: One study found that higher levels of the chemical in homes was linked lower sperm counts.

The long-term effects painting your nails with polishes containing TPP are not clear. To be safe, use nail polish brands that don’t contain TPP. Some are as inexpensive as $10 and can be purchased at your local beauty store.

And if you’re still worried, just stick to painting the town red, and give your nails a break.