You'll definitely want to avoid any silicone teether that contain BPA, PVC, or phthalates. Why?

1. BPA or bisphenol

-A is a plastics chemical that mimics estrogen and disrupts the body's hormonal systems. It's particularly harmful for pregnant women, babies, and young kids. Though most regulatory bodies, including the FDA, will tell you BPA is safe in the small quantities that appear in plastic products, many companies have chosen to produce and market BPA-free plastics. Excellent! Except for one small detail: Many companies simply replace BPA with BPS — bisphenol-S — which is just as toxic, if not more toxic, than BPA. Bottom line? Just because a product is touted as BPA-free doesn't mean it's safe.

‍2.PVC or polyvinyl chloride

The third most common plastic in the world — and also the most toxic. It's bad stuff, and you definitely don't want it in something your kids will put in their mouths.

‍3. Phthalates 

They are chemicals added to plastics to make them soft and supple. (PVC is actually hard and brittle so to make something like a squeezy toy requires the addition of phthalates.) Phthalates don't bond to plastic, though, so they leach out over time. Babies who suck on teethers containing phthalates will be ingesting a known carcinogen. Baby Center has an excellent list of phthalate names so you can check labels.