^I found an answer to that question on Women's Voices for the Earth
in the Science section:
"Q: I’ve read that O.P.I’s polishes do not contain and have never contained formaldeyhde. But I just bought an O.P.I. nail polish and read the ingredients, and it contains formaldehyde resin. Clearly O.P.I. is not as concerned about the health of their consumers as they so claim in their statement from 2007.
A: Great to see that you are checking labels and eager to keep these companies on their toes! We had the same question for OPI a while ago, when we also noticed the inclusion of “formaldehyde resin” in their ingredients.
Turns out, formaldehyde resin and formaldehyde are quite different things. While there is good science showing that formaldehyde exposure can lead to health problems (including cancer), formaldehyde resin does not appear to have the same effect. As I understand it, formaldehyde is used to make formaldehyde resin, but the resulting resin does not actually contain any formaldehyde.
Here are two links to the Skin Deep Database describing the potential health impacts of these two ingredients:
Thanks so much for your attention to detail. Hope this answers your question about OPI’s ingredients."