Hair falling out is one of the classic anxiety dreams, read as a fear of losing control, attractiveness or vitality. Hair coming out in handfuls is usually linked to stress that feels like it is slipping through your fingers, while a few strands on a brush point to smaller, steady worries. Watching it fall out in front of others is read as a fear of being seen at a weak moment. It reflects strain rather than anything about your body. It can help to notice where in your days you feel you are losing your grip.
Has this come up in your dreams before? What was going on in your life then?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.