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It's Time to See Your Internist

What's going on: There are a handful of health conditions that can lead to hair loss, including thyroid issues and autoimmune conditions. In fact, the most common cause of hair loss that Nazarian sees is alopecia areata, a localized form of hair loss (think quarter-size bald patches) caused by your body's immune system attacking your hair follicles—experts aren't exactly sure what triggers it, but it's believed that genetics play a role.

How to fix it: Talk to your doctor to see what internal issues could be leading your hair to fall out. With some issues, like lupus, the hair loss may not be reversible, but Hirsch says that most commonly, once you solve the underlying problem, your hair will return to normal. With alopecia areata, the most common course of treatment is topical or injectable steroids applied to the affected area.