Common warts (verruca vulgaris) are benign skin proliferations caused by infection of the epidermis with human papillomavirus (HPV), most frequently types 1, 2, and 4. Verruca vulgaris lesions may be acquired from direct contact with HPV-infected skin or, less commonly, from contact with HPV-carrying fomites. Autoinoculation is very common. Warts are frequent at locations that are traumatized. HPV types 2 and 4 may infect virtually any epidermal surface, including mucosal surfaces, but common warts are most often seen on the hands, feet, and knees. They may occur in tattoos.

Verruca manifest as skin-colored, hyperkeratotic papules. They may be pruritic, and scratching can produce a linear array of lesions via autoinoculation. Verruca vulgaris lesions are more prevalent in children and in immunocompromised patients; widespread, persistent lesions may be a clue to an underlying inherited or acquired immunodeficiency.

For unknown reasons, the incidence of common warts is approximately twice as high in White patients as in individuals of African descent and 10 times more common in Hispanic patients than individuals of African descent. In persons of African descent, the majority of warts are solitary, while most Hispanic patients present with multiple warts.

Immunocompromised patients often demonstrate larger confluent verruca that are more resistant to standard therapies. The presence of warts per se is not a reason for expensive immunological testing, however.