Liz Buchanan BVSc MRCVS
Hello and thank you for this interesting case. Dogs can self-harm for a variety of reasons; common ones include parasites (its quite common to see dramatic effects from fleas or sandflies, for example, without ever seeing the guilty critter) or allergies, or pain. This last one is often overlooked, but I have certainly seen dogs biting their paws to distract themselves from abdominal pain, for example. Regarding allergies, the frustrating news is that dogs can develop them; they can occur seemingly randomly at any age. They can also develop due to miniscule changes in the environment that owners don't necessarily notice, including for example a new plant sending its pollen over the fence, or a certain insect, or something they sniffed on a walk. In conclusion then, there's loads to go at and your vet should help to releive the symptoms and narrow the possible causes down.