Tingly, I wonder that also. Plus, any soap at all that gets in the bath water can increase the pH of the water and if it gets inside you, might change that delicate balance in the vagina that occurs with menopause.
I would like to just soak in a bath with no soap, but I am too afraid to try it because of my experience.
I cannot go swimming or sit in a hot tub either. Strangely, going into the ocean doesn't bother me!