Warts are painless, small, thickened areas of skin caused by one of the many varieties of papilloma viruses. They consist of outgrowths of fibres or layers of the true skin, which are enveloped by a cap of horny cells or thickened cuticle. They most often occur on the hands or feet and are usually harmless; genital warts are often more serious. Warts occur when the virus enters skin cells, causing them to rapidly multiply. These viruses can be picked up from contact with infected skin cells.
There are several varieties : (a) Common warts develop on children and young persons, often in positions where the skin is exposed to much irritation, for example on the knuckles; (b) Plantar warts occur on the soles of feet and are most commonly found in older children and adolescents. They are usually painful. Epidemics are not uncommon in schools; (c) Senile warts are usually, hard, wrinkled, and slightly raised areas of skin found in old people; (d) Soft warts, consisting of little tags of skin, are found especially on the neck, chest, ears, or eyelids; (e) Horns, occasionally reaching a length of some centimetres, are formed sometimes upon the face or hands, as the result of the drying up of the sebaceous material exuding from the skin that covers a wart; (f) Tuberculous warts are developed sometimes as the result of a wound in the skin of the hands, especially of those who have come in contact with persons or animals suffering from some form of tuberculosis; (g) Genital warts appear on the external genitalia, and sometimes inside the vagina, are sexually transmitted and may be quite painful.