Religious traditions across the world treat menstruation as spiritually significant, and the two most common framings, ritual impurity requiring restriction and spiritual potency requiring respect, appear both across different traditions and, in more complex forms, within single traditions at once. Jewish law observes niddah, a period of ritual separation during and after menstruation ending in immersion in a mikveh, a purity framework with its own extensive legal literature rather than a simple prohibition.
Many cultures across Asia, Africa, Oceania and the Americas restrict a menstruating woman's contact with sacred spaces, food preparation or ritual objects, restrictions this atlas records where attested rather than assumes as universal, since practice varies enormously by tradition and period. Alongside restriction, a distinct thread across the same range of cultures treats menstrual blood or the menstruating state as a source of unusual power rather than mere danger, associated in some traditions with fertility magic, prophetic capacity or heightened spiritual sensitivity, a reading anthropologists increasingly argue is not simply the opposite of the purity framework but is often present within it, since what must be carefully managed in ritual systems is regularly also what is understood to carry unusual force.