Answer: In the previous Halacha we have explained that before washing one’s hands for a bread meal, one must make sure that there is no substance stuck to one’s hands that will cause a separation between one’s hands and the water. Any substance which constitutes a “separation” regarding immersion in the Mikveh constitutes a separation regarding Netilat Yadayim, as we have discussed.
We have written additionally that something which does constitute a separation (on a minority of the surface area of one’s hand) but is not usually removed, such as a small amount of dirt caused by dust and the like, and is stuck to one’s fingernails on the part of the nail which is attached to the skin of one’s finger does not constitute a halachic separation since it is considered part of one’s body. (See Responsa Igrot Moshe, Yoreh De’ah Volume 1, Chapter 97)
We must now establish whether or not nail polish applied to a woman’s fingernails is considered an external separation and must be removed.
The Opinion of the Rashba
The source of this matter is quoted in the Responsa of the Rashba (attributed to the Ramban, Chapter 124) where he writes that if women dye their hands for beauty, this does not constitute a separation, “for it is meant to beautify them and they are not careful to remove it; on the contrary, they wish for it to remain. Furthermore, this color has no tangible substance.” Based on his words, we find two reasons to be lenient regarding women who would color their hands: The first reason is because women are not meticulous to remove it and actually wish for it to remain and can certainly not be considered a separation. The second reason is because this coloring had no substance (i.e. it would be completely absorbed by the skin and had no noticeable tangibility similar to hair dye) and therefore does not constitute a separation.
Nail Polish Applied Nowadays
Regarding the nail polish women regularly apply nowadays, it seems that they are not careful to remove it; on the contrary, they wish for it to remain (this applies only when the polish is completely intact and not when it is broken or chipped in which case a woman will certainly remove it). Nevertheless, the second reason of the Rashba about not having “tangible substance” clearly does not apply to the nail polish used nowadays which does indeed have substance as it creates a tangible layer of color on top of the nail.
The Letter of the Law Regarding Netilat Yadayim and Immersion in the Mikveh
Halachically speaking, according to Maran Ha’Shulchan Aruch (Chapter 161, Section 2), anything which one is not careful to remove and, on the contrary, wishes to remain on one’s self need not be removed, even if it has tangible substance.
Thus, as long as a woman wishes for the nail polish to remain on her fingernails and the polish is not broken or cracked as a result of having been applied for a prolonged amount of time, this does not constitute a separation regarding Netilat Yadayim and a woman may wash her hands with nail polish on her nails.
Nevertheless, regarding immersion in the Mikveh, a woman should certainly preferably take care to remove the nail polish from her nails (both fingernails and toenails), for regarding this issue, the custom of all Jewish women has been to remove all foreign substances from their bodies, even if it does not constitute a halachic separation. Only in specific situations where the woman wishes to immerse specifically in this way, while wearing the nail polish, may she be permitted to do so as Maran Rabbeinu Ovadia Yosef zt”l has ruled. Nevertheless, immersing in such a manner does not conform with the custom of modest Jewish women.
Summary: A woman who has nail polish applied to her fingernails may perform Netilat Yadayim with the polish still on her nails as long as she wishes the nail polish to remain and does not wish to remove it at that time. There is likewise room for leniency with regards to immersing in the Mikveh in this manner in extenuating circumstances, when there is no other alternative.