Black spots on the feet can be caused by diabetes, plantar warts and foot melanoma, according to the Society of Chiropodists and Podiatrists, WebMD and Medical News Today. Diabetes and foot melanoma are serious conditions that require medical attention.
Warning signs of diabetes include changes in skin color on the feet, especially if skin turns from red to blue to black. Patients should watch for a red or black spot within a callus or corn on the foot, notes the Society of Chiropodists and Podiatrists. A change in skin color delineates a lack of circulation to the feet commonly caused by diabetes. Black spots on calluses and corns should be examined as soon as possible for localized bleeding under the skin caused by excessive pressure. These spots may become ulcers if left untreated, and ulcers require more complicated treatment regimens.
Plantar warts on the feet may contain little black dots due to blood vessels growing within the warts, according to WebMD. Plantar warts, or seed warts, are caused by viral infections on the surface of the skin. These types of warts are not harmful and usually go away within two years without treatment.
The first warning sign of foot melanoma is a change in the color of moles on the foot. Most areas show blue or blue-black areas where melanoma is present, notes Medical News Today. Foot melanomas are also irregular, abnormal and swollen areas of the foot that may not heal right away. This type of black spot may denote skin cancer.