Male pattern baldness (MPB) is characterized by the loss of hair primarily in the areas of the temples and the top of the head. A more radical form of testosterone, known as dihydrotestosterone (DHT) is the trigger for MPB. DHT kills the hair follicles, which causes the hair to fall out. The temples and the top of the head are the primary targets for DHT because DHT receptors are concentrated in these areas.
The drug minoxidil, sold under the name Rogaine, was originally being tested as a treatment for high blood pressure as a dilator of blood vessels. The drug failed for this purpose. A noted side effect though of the drug was increased hair growth in some of the test subjects. Therefore, minoxidil was marketed instead as a hair loss remedy for both men and women.
Minoxidil works by increasing blood flow to the hair follicles. It does have some serious side effects though, which includes liver damage.
Increasing blood flow to the scalp to assist hair growth is hardly a new idea. People have long used irritating herbs such as cayenne pepper to stimulate circulation to the hair follicles. Brushing the hair preferably with a boar bristle or wood brush also does a good job of stimulating scalp circulation. Scalp massage is probably the easiest method to stimulate blood flow to the follicles. Not only does it feel great, but it is free and it does not damage the liver.
Keep in mind though that if the hair follicle is dead that increasing blood flow to the scalp will not bring it back to life. If there are still fine, living hairs present then there is a chance to regrow the hair.