While the causes of alopecia are systemic, the origins of damage to the hair structure - insofar as they are not of genetic cause - lie exclusively in external influences, which can be mechanical, chemical or physical.

Mechanical (E.G. combing, extreme brushing, back-combing, fastening with elastic bands, etc.)
Chemical (E.G. tints, bleaches, dyes, perms)
Physical effects (E.G. excessive heat from haidryers, intensive exposure to sun or UV rays)