Despite what you may have heard, too much brushing can actually fracture the hair, causing it to fall out. Fragile, dry hair is even more vulnerable to excessive brushing. Always brush hair gently and never when it is wet (use a comb, carefully, when hair is wet). The type of hairbrush you use is important, too. Boar-bristle brushes or "vent" brushes are good choices, since their rubberized tips don't pull the hair excessively.