Similarly to humans, dogs are susceptible to skin allergies and the result can be a very distressing time for both the dog and owner if it not treated quickly. Fortunately identifying the dog allergy symptoms is not terribly complex with a quick cursory glance at the dog usually being enough to prompt an assumption of allergy.
A dog skin allergy can prove particularly distracting to the dog with the rubbing and scratching taking over any other coherent thought the dog might have. The scratching can also progress to the point where the dog has rubbed all of its fur off of the back. At this point you run the danger of the wounds becoming infected and a further more serious illness might follow.
To avoid an escalation in the damage that an allergy may cause to your dog, do the humane thing and get it treated as quickly as you possibly can.