Plantar warts are often similar to calluses or corns, but can be differentiated by close observation of skin striations. Feet are covered in friction ridges, which are akin to fingerprints of the feet. Friction ridges are disrupted by plantar warts; if the lesion is not a plantar wart, the striations continue across the top layer of the skin. Plantar warts tend to be painful on application of pressure from either side of the lesion rather than direct pressure, unlike calluses (which tend to be painful on direct pressure, instead). Prevention HPV is spread by direct and indirect contact from an infected host. Avoiding direct contact with contaminated surfaces such as communal changing rooms and shower floors and benches, avoiding sharing of shoes and socks and avoiding contact with warts on other parts of the body and on the bodies of others may help reduce the spread of infection. Infection is less common among adults than children. As all warts are contagious, precautions should be taken to avoid spreading them. Recommendations include: Cover them with an adhesive bandage while swimming Wear latex swimming socks Wear flip-flops when using communal showers Do not share towels. Plantar warts are not prevented by inoculation with HPV vaccines because the warts are caused by different strains of HPV. Gardasil protects against strains 6, 11, 16, and 18, and Cervarix protects against 16 and 18, whereas plantar warts are caused by strains 1, 2, 4, and 63. Treatment A number of treatments have been found to be effective. A 2012 review of different treatments for skin warts in otherwise healthy people concluded modest benefit from salicylic acid, and cryotherapy appears similar to salicylic acid. Medications Salicylic acid, the treatment of warts by keratolysis, involves the peeling away of dead surface skin cells with keratolytic chemicals such as salicylic acid or trichloroacetic acid. These are available in over-the-counter products, or in higher concentrations, may need to be prescribed by a physician. A 12-week daily treatment with salicylic acid has been shown to lead to a complete clearance of warts in 10–15% of the cases. Formic acid, topical, is a common treatment for plantar warts, which works by being applied over a period of time, causing the body to reject the wart. Fluorouracil cream, a chemotherapy agent sometimes used to treat skin cancer, can be used on particularly resistant warts, by blocking viral DNA and RNA production and