Is it permissible to soak one’s foot on Shabbos or yom tov , in cold water, to relieve the pain of a rash?
One can soak the foot in water. On Shabbos one can wash one’s face, hands and feat in water heated up on erev Shabbos and on Yom Tov it is even permissible to heat up water to wash one’s face, hands and feet. Refuah Shlemah!
O”CH 326:1, 511:2