Minoxidil and ​Shedding: Why does minoxidil cause shedding?

Why does minoxidil cause shedding?

Minoxidil commonly causes increased hair shedding in the first 6-8 weeks of use (and sometimes a bit longer).  

Every human has hairs on their scalp that are destined to come out next week, the week after and the week after that. When minxodil is applied to the scalp, many of those hairs simply come out earlier than they are supposed to. This is termed "immediate telogen release" and is the main mechanism by which minoxidil causes shedding in the first 2 months of use.