Dear trumpedude,

It's not unusual for girls and women who live closely together — like mothers and daughters, sisters, or roommates — to get their menstrual periods around the same time. It's sometimes called "menstrual synchrony."

Synchronized menstruation is not understood completely. Many researchers think it has to do with substances called pheromones. Pheromones are natural chemicals that are emitted as odors from the body, although we are usually unaware of actually smelling them.

Pheromones affect many different aspects of our sexuality, including menstrual cycles and sexual attraction. It is believed that women living very closely with one another are affected unconsciously by the various pheromones they release during different phases of their menstrual cycles. Their cycles may become more and more similar over time. There are also other theories for why this happens.

Hope this information helps!

Take care,

teenwire.com^® Editors

This column is for informational purposes only and is not intended to constitute medical advice, diagnosis, or treatment. If you have a medical problem, please call toll-free 1-800-230-PLAN for an appointment with the Planned Parenthood health center nearest you.