Details in the Law of Intermediate Days of Festivals
Question
Is it permissible to remove facial hair for beauty during the intermediate days of festivals? Is it permissible to wash underwear? And what about in a washing machine? Is an undershirt considered underwear in this case? Is it permitted to wash it?
Answer
Shalom and joyous festivals!
A woman is permitted to remove facial hair during the intermediate days of festivals for the sake of beauty.
It is forbidden to launder during the intermediate days of festivals, regardless of whether it is underwear or other clothing. However, if all one's clothes have become dirty and one has nothing to wear, it is permitted to wash the minimum that is necessary for the festival.
What is permissible to wash, is also permissible to launder in a washing machine.
As for an undershirt, the same applies.
Source
Shulchan Aruch, Orach Chayim 534