Ulcers are areas in which the skin has eroded, creating an open wound. They are often round and crater-like, may leak fluid or blood, and the skin around the ulcer may be red, inflamed, tender to the touch, and in some cases, very painful. Ulcers may affect just the surface layers of skin, or they can extend deep into the underlying dermal layers or even into the fat layer beneath the skin. The most common types of skin ulcers are stasis ulcers and pressure ulcers.