Most of the allergic disease that occurs in dogs and cats affects the skin.
Horses also express allergy through both the skin and respiratory tract, in about equal proportions.
The dermatologist can also provide help to respiratory allergy patients by offering allergy testing services, which few internal medicine specialists are set up to provide. Parasites of the skin. There are many diseases of the skin caused by parasites which may include fleas, ticks, mange mites, biting flies and mosquitoes, and juvenile forms of parasitic worms. Infectious diseases of the skin. These include a wide range of bacterial, fungal, viral, and protozoal diseases.