Is it permitted to wear nail polish on the fingernails?

Greetings,

1. It is permitted, and there is no concern of a barrier with handwashing, as the Shulchan Aruch writes (siman 161, seif 2): and this is its wording: likewise, women who customarily paint their hands for adornment and the like, that color is not a barrier.

However, this is only when the nail polish is done perfectly. But if it is not completely full, and you would not go like that to an event, it is a barrier for handwashing (see Sefer Shiurei Shevet HaLevi, siman 198, seif 17, s.v. u-veTzivva, and Sefer Hilchot Olam, part 5, page 166).

2. However, regarding the immersion of a married woman - ideally, one should follow the custom of women to cut the nails before immersion. In any case, a woman who immerses with neat nail polish without cracks does not have a concern of a barrier, but she should at least take care to clean היטב any dirt found beneath the nails.

Sources: See Responsa Yabia Omer, part 2 (Yoreh Deah siman 13), Sefer Taharat HaBayit, part 3 (2019 edition, pages 27-28), and Sefer Shiurei Shevet HaLevi there.

With blessings,

Hillel Meirs