Best prevention I've found is to minimize stress levels, though. Haven't had any issues since I left my old job a couple years ago (used to find a new bald spot once every few months).
It's relatively cheap if you want to try it and see if it does anything for you.
I have some recent-ish photos (made in the last two to three years) on my blog. But I have located only one photo from a few years ago. It was made under very dark conditions and really does not show anything. For one thing, it is too small. A confounding factor is that my hair goes readily blonde, so I look wildly different from one photo to the next, depending on a lot of factors.
This is the only old photo of me that I know I have: http://2.bp.blogspot.com/-v4b3_qtrnP8/UvlaGATv1UI/AAAAAAAAAQ...
This should be all the posts with pics of me on my blog: http://micheleincalifornia.blogspot.com/search/label/Selfie