Genetic and hormones are the main culprits of hair loss. One leading form of hereditary hair loss in men and women is Androgenetic Alopecia (otherwise known as pattern baldness), which is responsible for 95% of hair loss. Androgenetic Alopecia is characterized by receding hairline and thinning from the crown of the head in the shape of a horseshoe.

With Androgenetic Alopecia hair loss is caused by an increase in testosterone, which leads to too much dihydrotestosterone (DHT), a derivative of testosterone. DHT can cause the blood supply that feeds the hair to become damaged, and it can eventually thin the hair follicle, causing hair to grow out thinner and shorter, until the follicle withers away. Furthermore, the body's immune system senses the follicle is dying, and as part of its defense system tries further to shut it down and get rid of it.

Other lesser causes include immune system disorder which leads to Alopecia Areata. This condition causes patches of hair loss on the head and sometimes over the body. Another condition is a stress or trauma-induced hair loss called Telogen Effluvium where hair growth slows, or hair thins or sheds over a period of time. Fortunately this shedding is natural, such as after childbirth, and is temporary and reversible.

Other temporary hair loss causes include lack of nutrition to the hair, lack of circulation to the hair root, scalp infection, or medical treatments/ conditions. Furthermore, product buildup on the hair root, and deep dirt on the hair root, when mixed with sebum, oxidizes into a thick hardened substance on the scalp, which then clogs the entrance of the hair follicle and blocks nutrient absorption by the follicle. The new strand of hair has to fight through the clogged follicle, resulting in a thinner hair strand and smaller bulb at the root of the strand each time the old one falls out. The end result is a hair follicle so damaged from bacteria, sebum and DHT production that the follicle dies.

Women's hair loss tends to be caused by product and dirt buildup on the root, lack of circulation and nutrition, irregular hormone levels and stress. After menopause women become more vulnerable to DHT hormones when their declining estrogen level is not enough to counteract testosterone and DHT, contributing to hair loss.

For men the number one cause of hair loss is DHT. Other factors may include lack of nutrition to the hair or sebum on the hair root.