Hair loss in a dream often reflects a felt loss of vitality -- energy, attractiveness, or youth you're afraid is slipping away. It can surface during a period of real vulnerability, when you're worried about how visibly you're aging or how much control you actually have over that process.
Understand the simple qualities of the Planets, for from thence thou shalt know all their mixt significations. - William Lilly (1602.-1681.)