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What Causes Warts to Appear?

According to the website Dermatology Channel, common skin warts are the manifestation of an infection of the upper layers of the skin by the human papilloma virus, or HPV. The website explains that the incubation period of a wart is 2 to 5 months following infection, after which a skin growth slowly develops. Although Dermatology Channel describes warts as common, it also indicates that at least 50 percent vanish within 2 years.

  1. HPV Strain

    • Dermatology Channel indicates that the particular strain of HPV with which someone comes in contact can determine the likelihood of infection, as well as where or how the resulting wart is likely to appear. There are more than 80 known strains of HPV; most strains can infect the skin, but contact with some strains does not result in warts. Two strains that produce different types of warts are verruca vulgaris, which causes raised warts, and verruca plana, which causes flat warts. The verruca plantaris strain is more likely to result in foot warts, and the condyloma acuminata strain causes genital warts.

    Immune System

    • According to the WebMD website, while some people have an immune system that can fight off epidermal HPV infections, others do not. Children, who have weaker immune systems than adults, are more inclined to warts. Warts are also congenital, meaning that if one member of a family develops warts, there is a likelihood other members of that family will develop them. This genetic inclination may result from similarities in each family member's immunity to HPV.

    Contact

    • WebMD affirms that warts spread through physical contact--by shaking hands, for example, or by touching an object someone with an infection has touched. Cuts and abrasions make the spread of warts more likely. Examples include scrapes, fingernails bitten or cut too short and nicks from shaving. Dermatology Channel says the HPV virus also can enter the skin through moist, cracked and peeling skin. New warts contain a higher concentration of the virus and are thereby more contagious than older warts.

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