Menstrual impurity is among the most important religious practices in Jewish lore. Examining two case studies of Judeo–Spanish Ottoman Jewry: discussions of the temperature of the ritual bath water; and purity, hygiene and the collective of the Jewish body, this article demonstrates that menstrual impurity in Ottoman Judaism underwent an intensive medicalisation process. This process reframed menstruation from a religious concern to one involving medicine, health and hygiene. This article offers a glimpse of how non‐Western Jews dealt with European conceptions of medicalisation, actively debating them according to their Ottoman cultural surroundings. Moreover, it illuminates the mechanisms women used to negotiate their immersion and command their own bodies, emphasising their anxieties, demands and resistance.