Hair loss is always dismaying, no matter where it happens—and it doesn’t always happen in the same place. Most often, we think of hair loss in terms of the scalp, but it can also happen on the face. In particular, men and women alike can struggle with eyebrows that thin, shed, and bald—leaving a feeling of self-consciousness behind. The question is, what actually causes eyebrows to get thin—and what can be done to prevent it?