Skin ulcers can be caused by infectious diseases such as shingles and impetigo. It may also be caused by non-infectious diseases, such as frostbite and diabetes. 1. Infectious diseases: skin ulcers may be caused by infections, such as herpes zoster is a varicella zoster virus infection, impetigo is caused by bacterial infections, may appear pimples and blisters, pustules, skin breakdown can gradually form ulcers. 2. Non-infectious diseases: may be caused by frostbite, due to long-term in the cold environment, local blood circulation disorders, resulting in redness, swelling, and even necrosis, skin ulcers. May also may be caused by diabetes, patients often have foot pain, numbness, skin temperature reduction and other symptoms, may be combined with infection, ulcers, gangrene, which manifested as skin ulcers. There are many causes of skin ulcers, and patients are advised to go to the hospital and clarify the cause.