Wart on a man's finger. A wart is a contagious but harmless skin growth. It is caused by the human papilloma virus (HPV). There are over thirty different types of HPV. Warts can disappear spontaneously within a year. Warts can be removed with chemicals or lasers, by scraping (curettage), by freezing (cryotherapy) or by burning (cautery). The growth of this wart underneath the finger nail is impeding the growth of the nail. Photographed in Africa.