I know that it is common for a group of
women that spend a lot of time together to eventually have their periods
the same time of the month. Could you give me a scientific explanation as
to why this is the case? It has happened with my wife, sister, and
mother-in law in the same house, and also with a bunch of different women at
work who all sit next to each other. Does it have something to do with
To my knowledege no one yet knows...pheromones?
This topic has surfaced a number of times with much speculation. Pheromones do
regulate reproduction in insects species and it has been hypothesized that it
may play a role in all mammals as well.
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Update: June 2012