Today women's hair loss carries with it significantly more social stigma than hair loss in men, so for many it comes as a surprise to learn that it's nearly as common in both sexes. There are however a number important differences, including the main causes.
If you're looking for answers the best place to start is with your family tree. Most instances of female hair loss are the result of genes inherited from both parents. Dermatologists dub this cause of hair loss androgenetic alopecia , which more specifically relates to the interplay between your genes and your androgens ('male' hormones which are also present in women - although at much lower levels). The female hormone estrogen is thought to counteract the male androgens, which helps to explain why women start loosing hair later in life than men (and commonly when their hormonal balance is upset, such as after the menopause).
A second cause comes under the broad scientific umbrella of telogen effluvium . For anyone who's forgotten their Latin; telogen refers to resting (of hair growth) and effluvium to an outpouring. When the body undergoes stress hair follicles often stop growing while the body deals with the trauma. Once everything's back to normal, and the hair cycle starts up again, the resting telogen hairs are shed en-masse (the effluvium bit). As the hair cycle takes a while to get going hair loss typically occurs months after the trauma. Common stress triggers include; childbirth, crash diets, surgery, illness and family bereavement. In most cases hair will grow back once the cycle is re-established, but not always.
Alopecia areata is the most devastating cause of female hair loss and is thought to be the result of the immune system turning against the body's own hair. This can mean anything from localized bald patches to the body rejecting all hair. There's still a great deal to be learned about the condition, and if you are in any way concerned book an appointment with your doctor or dermatologist.
Several other factors have been implicated in female hair loss, including hormonal change and the effects of certain prescribed medicines.