Not enough is known about the science of pads and tampons

reproductive system has an entire branch of medicine, gynaecology, devoted to it. Yet all that effort has more or less neglected a quotidian matter that really ought to be investigated properly. Or rather, not a quotidian matter, but a menstrual one. At any given time, about 300m of the world’s women are menstruating. Of these three-quarters will be using some sort of menstrual product—tampons, pads, pantyliners, cups, period underwear, discs and so on—to regulate their flow. An average woman who employs such devices will use around 15,000 of them during her life. Someone with abnormally heavy periods might need thousands more. And many women wear several products simultaneously, for extra protection. Moreover, the skin of the vulva, the vagina’s external protection—which comes into direct contact with pads and pantyliners—is one of the body surface’s most sensitive parts. It is more permeable than the rest of the epidermis, and becomes still more absorbent when irritated. And the vaginal canal, where tampons sit, is lined by mucous membranes supplied by blood vessels that absorb chemicals into the bloodstream without metabolising them.