A relatively new personal hygiene product that a woman can wear during her period instead of pads and tampons, or she might wear them as a backup. They typically are made of several layers of cotton, nylon, merino wool or polyester that are designed to hold period flow. They may also contain potentially harmful chemical compounds called PFAS or short chain per-and polyfluoroalkyl substances. Assuming they are not giving a woman cancer or causing infertility, liver damage, thyroid disease, or other physical problems, period underwear wick flow and moisture from the vulva so the wearer feels dry. If a woman lives long enough and does not put them in a dryer, period underwear can last for years. They do have a steep up front cost— about the same as a box of 40 tampons, but they appear to be more enviornmentally sound. Another environmentally sound alternative that doesn’t contain potentially harmful chemicals is called a menstrual cup