Warts are caused by a virus. The result is an often hard, unsightly callus with an unusual texture. Dark spots may be noted within the body of the callus, and if picked at or disturbed, they may bleed. This is in contrast to a friction or pressure callus, which is simply thickened hardened skin or epidermis. A callus that is pared or shaved down rarely bleeds whereas a virus almost always does. A friction or pressure callus is not contagious, but a virus is. Sometimes a wart presents as a single lesion, and over time they may spread to many or even cover the entire plantar (or bottom) surface of the foot or toes.

Treatment is usually started with a topical mild acid (salicylic acid, 20 to 40%) or cryotherapy (freezing with dry ice or other cold products). If this doesn’t work, laser therapy with or without excision under local anesthesia often will. Some wart cases are very stubborn, and although they may take years to go away, are not serious and almost always a benign lesion. Biopsy can be performed at any stage to confirm this type of lesion.