As with most skin conditions, it is important to get your dog checked out by a vet if the cause is unknown. One possible reason for this is contact dermatitis – with an indication that only one of your dog’s paws came in contact with the offending agent. Contact dermatitis can happen when the dog has had contact with items such as plants, metals, soaps, detergents, shampoos etc. causing an allergy. The affected areas are normally witnessed in the hairless parts of the body because the hair-covered areas are less affected.