The most common source of vicarious menstruation is :
High-Yield Explanation
Epistaxis during menstruation Menstruation may initiate nasal irritation or nasal allergy. This may be due to state of heightened nervous and vasomotor instability or due to pre menstrual fluid retention Ref:Disease of ear nose and neck, PL Dhingra and Sruthi Dhingra,Pg 177. Internet sources.