Sasha Piton was on a hike near her home in Idaho Falls, Idaho, when she realized something was wrong. The trek was just a few miles, and not strenuous, but a rash was spreading along the crease above her thigh. Ms. Piton quickly identified the cause. Like many members of the Church of Jesus Christ of Latter-day Saints, she wears a white two-piece set of sacred temple garments, which are functionally underwear, almost all of the time.