In the practice of hoodoo/rootwork/conjure, men are warned not to accept drinks or foods, especially dark colored drinks or soups or stews, from women who are strangers or who are suspected of being witches. One of the activities associated with witches is that they will sneak some of their menstrual blood into a man's food or drink in order to have power over him and control him.
Today the practice of sneaking menstrual blood into the food or drink of a man is being taught as if it is a standard and normal practice for female practitioners. In the past this belief was more of an urban legend or fear that men had. It was also a common belief that certain mothers had when they felt their sons had become enthralled with a bad woman. Thus the excuse was that the woman was at fault because she had dosed the son's drink and thus the son was blameless.