Dark brown warts are usually common warts or flat warts, which are benign growths on the surface of the skin that can be dark brown or brown in color and are caused by human papillomavirus infection. The black-brown warts are mostly benign, with no obvious symptoms, no pain, no itch, but they are contagious. When the human skin or mucous membranes are broken, the human papilloma virus can infect the skin in the area and form wart-like growths. Common warts and flat warts can be treated with Vitamin A ointment. Note that this medication is prohibited for people with skin lesions. You can also use laser, interferon, cryotherapy and other programs. It is advisable to consult a dermatologist in a hospital for the above symptoms, and a doctor should be consulted for specific medications and physical therapy.