In a lot of cases, dermatologists can trace your intense shedding back to "telogen effluvium," a hair loss condition caused by a big change in your body, which can be anything from stress to starting a new medication. "After an 'insult,' your body sends a signal to put all the hairs in the growth phase prematurely in the resting phase," Dr. Senna says. And then you lose it. Doctors know the patterns in which these inciting events lead to hair loss, but the exact reason why this happens is sort of a mystery, which is why it's important to take a holistic approach to treatment, explains Arielle Nagler , MD, assistant professor of dermatology at NYU Langone Medical Center. In other words, it'll be pretty tough for you to self-diagnose, so seeing a doctor and telling her everything that's going on with you will be crucial.