Sores And Hair Loss Repeatedly On My Mini Dachshund, What Could It Be?

It could be that he's had a reaction to the swallow, but you can't be sure. I would take him to another vet and see what they come up with. I'm not saying that you shouldn't trust your current vet, I'm just saying that maybe your current vet missed something that another one might see. Hope this helps, good luck.

I can't see a connection.  What were the x-rays for.. And what has your vet said about the itching/hair loss?  I'm wondering if he didn't pick up the skin issue from another patient while in the vets office. 
 
Read through  this page and see if anything fits... www.thepetcenter.com

Our dachshund breaks out every fall and summer. It is due to allergies. Have them tested. Ours was Beef. So we changed him to chicken. No more problems since.