Infected ulcer on the big toe of a 98 year old female patient. Foot ulcers are open sores that occur when an area of thickened skin is left untreated. They can deteriorate and lead to severe infection or gangrene. Common risk factors for developing this condition include ill-fitting footwear, injury, poor foot hygiene and diabetes. Treatment for foot ulcers can involve various steps such as taking the pressure off the area, removing dead skin and applying medication or dressings to the ulcer.