A hot spot is a patch of hair loss with oozing skin, hence the term “moist dermatitis.” It’s usually several centimeters in diameter and may actually extend under the fur for some way. They appear quickly, and it’s not unheard of for areas 6 inches or more across to appear overnight. The skin is often red through irritation and the ooze is typically pale yellow-white. The fur around the area is usually sticky with the ooze, so may clump and appear darker than usual.