Hereditary Hair Loss Explained

There are many potential causes for thinning hair, but heredity is usually the main culprit. Learn more about what that means for you, the other possible causes, and the different types of hair loss.


The average person is born with 100,000 hair follicles on their head, which are in a constant state of change. When a follicle is first activated, it grows thick hairs for several years. When the growth cycle is complete, the follicle undergoes a transitional phase before entering into a resting period where the hair is eventually shed, and the cycle begins again.

Hereditary hair loss starts with a progressive shortening of the hair’s growth cycle and involves gradually shrinking hair follicles that eventually are no longer able to produce normal hair.     


Hair thinning is surprisingly common. More than 1 out of every 4 women will experience it at one time or another. While certain lifestyle factors can absolutely have an impact on your hair’s thickness, over 90% of all hair loss is due to genetic factors. So before you start blaming your diet or blow dryer, get to know the facts behind the science of genetic hair thinning.


In general, hair loss falls into one of 2 categories: hereditary and non-hereditary. Hereditary hair loss is known as androgenetic alopecia (AGA) and is a genetic condition that shortens the time that the hair spends actively growing. AGA eventually  causes the hair follicles to slowly shrink. Women with hereditary hair loss experience a general thinning of the hair, with the most extensive hair loss occurring on the top of the head and along the part. The number of women with this type of hair loss increases with age, but it can start as early as your 20’s. Women’s ROGAINE® Foam is only indicated to treat hereditary hair loss.

On the flipside, temporary hair loss, known as telogen effluvium, happens when stress, diet, a hormonal imbalance, or a traumatic event causes the hair follicles to remain in the resting state, causing increased hair shedding and a temporary thinning of hair across the whole scalp. While the amount of time someone stays in telogen effluvium varies, once the imbalance has been corrected, the hair will return to its previous thickness.

A third kind of hair loss is called alopecia areata, an autoimmune disorder that is recognized by well-defined patches of hair loss, which may happen rapidly and can lead to complete hair loss. If you have no history of hair loss in your family and are experiencing this kind of hair loss, consult your doctor.

If you’re not certain about what kind of hair thinning you’re experiencing, our quiz can help you start to sort things out.


It’s a commonly held myth that genetic hair loss is only inherited from one side of the family or the other. In reality, you can inherit the thinning hair gene from either your mother or father (or both). That being said, if a number of close relatives have thinning hair, your chances of experiencing it increase, but are by no means inevitable.


Incorrectly thought of as only a male ailment, both men and women experience hair loss, but in varying patterns and severity. Men will tend to recede at the hair line and/or experience hair loss around the crown of the head, whereas a woman’s hair loss usually involves a more dispersed thinning on the top of the head, which may be especially noticeable as a widening part.