Baldness. Rear view of a completely bald head of a man suffering from generalised alopecia, a condition that results in the loss of large amounts of hair. The condition is caused when large numbers of hair follicles simultaneously enter their resting phase and then fall out about three months later. The hair regrows when the underlying cause is removed. This condition is usually caused by stress due to illness or surgery. The condition can also be caused by cancer treatments, such as chemotherapy or radiotherapy, as these can affect the dividing cells in hair roots.