My teen daughters love nail polish like many other girls. In general I have always been careful with them to let them only get natural cosmetics, because I am worried about all the chemicals entering through the skin. However, with nail polish I let them choose any brand, because I thought the chemicals would not get through the nail. I did have them apply it outdoors or in the bathroom with the window wide-open to minimalize the inhalation of fumes. More recently however, I did learn that the chemicals in the polish do enter the body through the nail as well!
The most worrying are these chemicals: toluene, dibutyl phthalate (DBP), formaldehyde, formaldehyde resin or camphor. Luckily as more costumer want to avoid these chemicals, there is an increasing number of brands that offer ‘5-free’ polish! I found some great lists of non-toxic brands on Ecowatch and KrisCarr. However, these are all American products, so I was very happy to find very affordable ‘5-free’ nail polish from the European brand Benecos at the Alnatura shop! They offer 18 fashionable colors at only €3.95 per bottle. I am giving my girls a few bottles for Christmas 🙂
Update from 2020: I rarely ever use nail polish myself, but my daughters still use this one regularly and it works fine!