Cysts and Blisters
This was a rescue that came in a week after being severely attacked by a cagemate. It turns out that the 'acne' above was from him rubbing against the cage floor due to his back leg being broken. Once the leg was healed, they disappeared.
Like any animal chins can develop cysts and infections under the skin. Most often they are seen around the jaw area and caused from malocclusion or pieces of hay embedded in the gums. On the rare ocassion they develop on other parts of the body and are like any normal cyst where a vet can lance and drain them with the chin suffering no further problems. These are often attributed to a diet high in sugar and starch.