Warts (sometimes known in Surgery by their Latin name Verrucae) are collections of lengthened papillae of the Skin (q.v.), closely adherent and ensheathed by a thick covering of hard dry cuticle. From friction and exposure to the air their surface presents a horny texture, and is rounded off into a small button-like shape. Such is the description of the simple wart, which is so commonly seen on the hands and fingers (and rarely on the face or elsewhere) of persons of all ages, but especially of children. Amongst other varieties of warts are (1) one to which the term Verruca digitata has been applied. It is more elongated in shape, and less protected by cuticle than the preceding. It is said to occur nowhere but on the scalp of women of adult age, and sometimes to occasion great annoyance in brushing and combing the hair. (2) Subungual warts, growing, as their specific name implies, beneath or at the side of the finger or toe nails. They originate beneath the nail, and as they increase they crop out either at the free extremity or the side of the nail, and are usually troublesome, and often very painful. They are generally of syphilitic origin. (3) Venereal warts, caused by the direct irritation of the discharges of gonorrhoea or syphilis, and occurring about the parts which are liable to be polluted with such discharges. They attain a larger size, and are more fleshy and vascular than other warts.
Nothing is known of the causes of warts further than that the third variety is induced by an irritating discharge, that the malignant form of wart which is the beginning of chimney-sweepers' cancer is caused by the irritation of soot, and that persons engaged in dissection and post-mortem researches are especially liable to them; hence we may infer that they are always due to some local irritation. Venereal warts are certainly contagious; with regard to others, we cannot speak positively. According to popular belief, blood from a wart is capable of producing similar warts when applied to the skin, and occasionally, but rarely, this has been the case in the experience of surgeons. In consequence of the capricious way in which warts often undergo spontaneous cure, there are numerous popular charms for their removal, several of which may be found recorded in the pages of Notes and Queries. Common warts are so apt to disappear that they may be often left to themselves. If it is desired to remove them, glacial acetic acid may be applied with a camel-hair pencil till the wart is pretty well sodden, care being taken not to blister the neighbouring skin. One or at most two applications are usually sufficient. Nitrate of silver and tincture of iron are popular and general applications. Salicylic acid in collodion (see CORNS) is also very effective. Small warts hanging by a neck may often be very simply removed by the tight application of an elastic ligature (e.g. a small broken elastic ring) to the base. The wart usually shrivels up and falls off within a week. The other varieties of warts must be left to the surgeon.