Key Social Norms Take-aways This study reveals how adolescent girls’ experiences of menarche and menstruation in rural Tamil Nadu are deeply shaped by cultural codes and gender norms. While the study does not use formal social norms measurement tools, it explicitly explores how norms are constructed, maintained, and reproduced through social practices, especially those related to gender. Girls reported learning rules around behavior, space use, dress, and interactions with men, often passed down by mothers and grandmothers. These gendered expectations were framed as a transition into womanhood, triggering restrictions, shame, and isolation. Menstruation was treated as both a biological event and a sociocultural marker governed by stigma and secrecy. The findings underscore how restrictive gender norms shape menstrual hygiene practices and psychosocial outcomes, reinforcing the importance of norm-sensitive approaches in WASH interventions.

Objectives To explore adolescent girls’ experiences of menarche and menstruation in rural Tamil Nadu, understand how these experiences are shaped by sociocultural norms, and inform the adaptation of a school-based WASH health promotion intervention (Project SHINE).

Methods The study used a qualitative, phenomenological approach informed by feminist theory. Ten semi-structured interviews were conducted with ninth-grade girls in two rural schools in Thirumalaikodi, Tamil Nadu, in June–July 2018. Data were analyzed thematically using Attride-Stirling’s framework.

Intervention Details Findings informed the adaptation of Project SHINE, a school-based WASH intervention, by introducing new activities focused on menstrual health. These included a classroom lesson and an extracurricular peer-to-peer activity using visual tools (e.g., Menstrupedia comics) to address knowledge gaps, myths, and stigma.

Results Menstruation was described as both celebratory (menarcheal rites) and distressing, often triggering psychological stress and social isolation. Girls reported secrecy around menstruation, fear of teasing, and shame. They adopted coping strategies like avoiding public spaces, concealing their status, and withdrawing socially. Gender norms restricted mobility, interactions with males, and participation in religious and household activities. Relationships with male family members often became more distant post-menarche.

Conclusions Menarche and menstruation act as key moments when gender norms are reinforced, introducing girls to a broader system of social restrictions. These norms affect not just physical practices but emotional wellbeing and social participation. The study demonstrates how formative research can unpack these dynamics and guide culturally responsive WASH intervention design to challenge stigma and support adolescent girls’ health and agency.