Why would a woman lose hair (start to bald in one spot)?

I'm thinking maybe the pony tail is too tight. What other reasons could it be?

Here are the some of the common reasons of hair loss-
stress=emotional or physical eg surgery
hormone reltd=thyroid dysfunction , pregnancy, menopause
medical issues= diabetes, lupus, fungal infection
drugs=chemotherapy,blood thinners,antidepressants,excess vit A
traction alopecia= pulling hair back too tight,cornrows,tight hair rollers...but it wouldn't be in one spot,it would look more like a receding hairline

She's going through menopause. She's losing estragon. See a doctor. They can help.

Stress causes people (men AND women) to lose their hair.

Alopecia areata (or 'spot baldness') is usually unexplainable, but can come from a number of causes such as poor diet (malnutrition causes hair loss), hormone changes (menopause), or follicle damage. She should probably see a specialist!

I t could be she needs her thyroid checked- she should make an appointment and explain this to the doctor.

Its partly because of genetics. I'm not sure of your age but a lot of older women get bald spots, just like men do. Thank God I have thick hair! lol

All of the above plus - some diet changes and drastic weight loss in a short amount of time can cause it. Some hair loss is temporary and certain kinds of hair loss in woman goes in cycles and the hair will grow back - other kinds like in men it is more permanent and will not grow back. Lucky for me mine grew back.

Could very well be. It tightens and constricts the hair.
Sould not wear it in a pony tail all the time. And especially when sleeping.
Might want to get special shampoo and conditioner for thining/badling hair.......
Sally's Beauty Supply carries them.
Also apply a hair masque.
Do this and see if it helps the hair come back.. It should
Give it some time of course..........

Yes, really tight pony tails or braids can cause you to lose hair permanently in one spot. A lot of black women will lose their hair in the front from really tight braids worn a lot when they were little. Never use rubber bands in your hair. They are bad to pull the hair out. After a while the hair doesn't come back and you are stuck with a bald spot.
On the other hand there is male pattern baldness. Women can inherit this from their fathers when they are older. And menopause causes hair loss too. There is a remedy for hair loss due to menopause. There isn't anything you can do for hair loss due to male pattern baldness though.