dog wanted a stroke but growled and bite me instead?

Hi i have had this dog for 13 years now, he has just had a health check from the vets and he was clear and healthy, but lately he has been growling and snapping at us. I dont know when or if he will do it, he mainly goes it, when he comes and sits next to me and nudges with his nose on my hands to stroke him, so i do after a stroke or two and in the same place he shows his teeth, growls and trying to bite me. eh? what is going on???he was checked last week and he has done this for awhile now, he runs all over the park chasing the ball, we have showered and bathed him (putting shampoo on him) and he didnt bite or anything, so i dont think its pain, as he would have gone for me, when i was rubbing in the shampoo.

When was this health check as was the dog doing this when he had the health check if not then get the dog checked again .Edit..A dog that suddenly does this and especially at that age must be in some kind of pain ,Your dog could have any number of things wrong that could eb causing pain .A check from the vet is not enough to diagnose unless tests Xray scans etc are performed .

When the dogs behavior changed like that, it was good you took him to the Vet. The Vet said all was well & fine & yet the dog continues to bite. It could be canine senility, you know how some people get mean & loud as they get older.I used to groom dogs & I specialized in dogs with behavioral problems. When I had a dog on the table & he stated to snarl, I would try to get my hands & fingers in its mouth, "Here, you want something to bite, bite this."& I would do this every time the dog snarls or lifted his flews. I taught the dog that biting my hand was not going to stop me from doing what I needed to do.A very serious dog would keep his teeth clinched very tight & I could not get in & I would have to correct the dog when it tried to bite. My correction for biting is a pop on the nose, or the tender tissue just behind the nose. Using just two fingers, there is no room to use more than 2 fingers. Now how hard to pop the dog on the nose depends on the intensity of the attempt.There is nothing there you can break. It is just tissue & grizzle. Your dog is not a mean vicious dog so your correction doesn't have to be all that hard. Some dogs only need a tap on the nose & some of the big dogs in aggression training , sometimes needed a fist. so it depends on your dog as to how hard the correct must be to stop the biting.

Your dog is ill as sometimes the health check doesnt show up everything, its just like a health check on humans some illnesses are not seen. As he is 13 he is getting on a bit. My Dobermann started to get grumpy at age 8 and had never been like that before and there was no obvious signs of illnesss however it turned out to be cancer so he must having been feeling unwell and it was strange as he was only grumpy when I stroked him on the hips and the cancer was in the lymph nodes not at the hips. I think you may have to just put up with it for now and try and work round it. I used to just walk away from my dog when he did that and ignored him for a while, I just accepted it until he died as I knew he didnt really mean it and it wasnt his fault. good luck.