Alopecia areata is hair loss which occurs in patches. It is not male pattern baldness, which is the normal sort of hair loss which many men will go through in there life. It is an auto immune disease, which basically means that it is where the bodies immune system is attacking the body. It can occur at any point in someones life. Generally what happens is that it is not a gradual process rather it strikes like lightening. These patches of hair which disappear tend to be round and the skin is smooth with little to no hairs present. It is not restricted to the head, it can also occur on the eyebrows or legs.
It is currently not exactly known what first starts this process off, it is thought that stress may be a trigger for this to happen, but for most people there seems to not be any particular reason.
This is done by calming the inflammation which is occurring due to the immune system attacking the hair follicles. Generally this is done using a steroid which is subcutaneously injected within the skin. This injection stops the hair loss process from occurring. After the attack by the immune system stops, the hair should regrow, but this can be from as little to a few months to years. Cortisone is one such steroid that has been prescribed before to treat this.