ODD symptoms with a dog I run..straight legs..excessive scratching at the neck..

Hi I am wondering if anyone has experienced these symptoms with their dog? I run a dog on the beach here locally. I've run him 30 min 1-2 times a week for about 4 years with no issues.  He recently has had some odd behaviors. His family took him to the vet and they are stating that its possibly an allergy. This does not seem right to me. His symptoms are: excessive scratching at the neck (both sides)Not the type you see with fleas. Its more intense. Its to the point where he falls over when he scratches...(like a nerve) A harness doesnt aggravate him as much as a collar and leash since this started happening. Whats most concerning is that he has stiff front legs when he runs and his front paws sometimes fold under causing them to bleed from getting scraped. Its very sad. He has no prior health issues. Everything else is the same for him. Energy level is fine. What could this be? Its been going on for a month. I'm afraid to run him. I dont want him to get hurt. I appreciate any information.

Hello and thank you for this unusual question.  First, remember that I haven't seen your dog (don't even know the breed) so I have substantially less information than the vet, who has examined the dog, their skin and so on.  However, there are some unusual cases that can look like this including a) fitting (partial seizures) b) pain responses eg displaced scratching from arthritis or c) neurological abnormalities, such as spinal signs  (paws folding under him) or brain lesions.   It may be worth asking the owners specifically to describe the stiff-legged episodes and the falling when scratching to their vet; if you have witnessed it, perhaps you could jot down what you saw in as much detail as you can remember.  This could prove to be crucial information and may change what they do.