Dogs often lick the floor because of simple compulsive behavior, a physical problem such as poor vision, parasites, gastrointestinal disorders or neurological dysfunction. There may also simply be food residue on the floor.
A study in the Journal of Veterinary Behavior indicates that dogs with obsessive behavior, such as continually licking the floor, often have ongoing medical problems such as irritable bowel syndrome. Another part of the study showed that 14 out of 19 dogs with obsessive-licking behavior stopped the action when their conditions, such as giardiasis, inflammation of the GI tract, chronic pancreatitis and delayed gastric emptying, were treated correctly and effectively. However, obsessive behavior does not always arise from a medical problem. Sometimes a dog might lick a wounded paw or another part of its body that is injured. Even though the condition heals, the dog may continue the behavior even on other objects, such as the floor. Obsessive behavior in dogs can result from various anxiety disorders as well, such as being separated from their owners or being confined in a tight place. Licking is a natural action for a dog, and it might naturally keep doing it as a way of comforting itself due to stress.