The problem more specifically:
She tosses her head constantly at the canter- other gaits are fine.
She will immediately jerk her head away if you touch her ears.
It started about 3-4 weeks ago. It has happened once before but it only lasted about 3 days or so.
Initially we assumed she had some parasite or bug or something, but a vet has looked at her ears and said there was nothing wrong with them. We are getting a second opinion tomorrow though because I'm pretty convinced there is SOMETHING the vet missed the first time.
The other barn's trainer also thought it might be allergies, but allergy medication hasn't made a difference. Another theory was that she didn't like the wind, since the slower gaits were fine. However, a bonnet thing didn't help either and she's sensitive about her ears being touched, and that's not really a wind issue.
Oh, and another thing- the problem started before we moved her to the barn where she is on trial, so the change in environment isn't what caused it.
If anyone knows what this could be, I would be so so so grateful if you guys could help me out. We really don't know what we're going to do with this horse if she doesn't sell.