The Shulchan Aruch (OC 551:3) rules that one may not do laundry during the Nine Days, because it's taking one's mind away from the mourning.
- Does this apply to doing laundry for medicinal purposes? Say that a person has dust allergies and needs to wash his pillowcase to get the dust off of it. Is that permissible? On the one hand, he's not doing it for pleasure; he's doing it out of necessity. On the other hand, so is washing your only set of clothes, which the Shulchan Aruch (same se'if) prohibits.
- If yes, is one allowed to wash other linens while he's at it? On the one hand, he's removing his mind from the mourning by washing it. On the other hand, the real reason he's doing the laundry is for medicinal purposes.