Here is a link that I think youll find interesting.
I have 2 horses that have done this, (both from the same mare.)
The Filly (now 4) would bite at hers sides, and kick out w her back feet violently, it seemed to come on suddenly. We chalked it up to hormones.....as it started when she started to come into her first heat)....when it didn't settle, we too thought ulcers....we had her scoped....nothing, came back clean. Then it seemed to subside once she started training. She does do it occasionally still, but not nearly as bad as she used to from a common occurrence, to know only occasionally.
Then my colt started it when he was about 8 months, but he would try and bite his flanks, and would spin so fast in a circle as he tried to reach his flanks, that he would almost fall over. It almost looked like he was chasing his tail. In his stall he couldnt spin, so he would back up in the corner and bite at his sides, just as his sister did.
I went through the same process w him as w my mare, by trial and error ruled out different things we thought it could be. My vet was involved but never really came to any clear answer, and actually was quite useless in the process....in her defense I think she had no clue what the issue was, as with me.
In a last ditch effort, I turned to Google.....and found Equine Self mutilation
. And the pieces started falling together.
Now both my mare (4) and colt (now 1 1/2) only have to occasional symptom. As I have cut out most concentrates from thier feed, and they both get Chammomille 2/day, and both are on a very regular work schedule. Granted my colt at just under 2 cant be worked, but he challange his brain other ways, such as hand walks over poles and games of that nature. Equine Self-Mutilation