The aim of this article is to analyze the fears about menstruation and health that have been passed down to us by oral transmission from a gender perspective. A qualitative study, whose design was the Grounded Theory, performed in Seville, Spain, with 24 rural and urban women from different generations, young (18-25, 26-35 years), middle aged (36-45, 46-55, 56-65 years) and elderly (> 65 years). The semi-structured interview was used as a data collection technique. The discourses were subjected to content analysis, following the steps of Grounded Theory. The results highlight the abundant fears related to use of water during menstruation, with very harmful effects to health. As a conclusion to highlight the lack of women's knowledge about reproductive health and that despite Health Education campaigns there are still ancient misconceptions present about menstruation.