Atopy, also known as atopic dermatitis, is a disease which can commonly occur in dogs. The effects of the disease cause allergic reactions which drastically affect the skin. Dogs with atopic dermatitis may suffer from a variety of symptoms which include: severe itching all over the body, sores on the paws and base of the tail caused by continual licking, hair loss, skin which becomes thick and takes on a leathery appearance, and a darkening of the color of the skin.