Warts are one of the most common skin conditions to occur in both children and adults, and they are usually easy to remove. A variety of warts exist, but they are all caused by an infection from a strain of the human papillomavirus (or HPV). Warts typically appear in those who have weakened immune systems, but can show up in healthy individuals who have come into contact with someone else who has warts, as the condition is fairly contagious. Characteristics of warts include slightly raised growths that protrude from the skin that are almost always benign, but can cause some social embarrassment. Warts are often removed for cosmetic purposes, but may be biopsied to ensure no forms of cancer are present. The removal process can be done by simple excision or freezing it with cryotherapy. Medications like salicylic acid or cantharidin are also effective at eliminating warts.