My patient Jim asked me to re-run my column about warts. They are very common—it’s estimated that up to 12 percent of people worldwide have had warts and that 10 to 20 percent of school-aged children have them at any given time.
Warts are caused by a group of viruses called human papilloma viruses (HPV). When people hear HPV they often think of genital warts that are caused by particular strains of HPV virus, some of which have been associated with cervical, mouth and throat cancers. There are over 100 known types of HPV, all of which share the characteristic of being able to infect skin cells.
Warts are spread by direct or indirect contact with another person who has them. People can also spread them from one body location to another. They commonly attack skin that is dry, cracked or has an open wound. The incubation period from infection to development of a wart is usually one to three months, but may take years.
The appearance of warts runs the gamut from small flat lesions to large, raised ones. Larger warts are typically seen on the palms or soles of the feet. “Planter’s wart” is common misnomer for a wart on the bottom of the foot. These warts have nothing to do with gardening or farming. The proper term is “plantar wart.” Plantar is the anatomic term for the bottom surface of the foot. These warts usually appear to have a central core or seed, hence their other common name, “seed wart.” These “seeds” are actually small blood capillaries that have clotted.
Warts can be difficult to treat, and simple over the counter remedies often work just as well as medical treatments. Treatment success depends on the size and location of the wart as well as the aggressiveness of the treatment. Large warts are usually covered by a protective callus that should be removed before applying treatment. Interestingly, 65 percent of warts may go away on their own within two years but a person always runs the risk of the wart spreading elsewhere in the meantime.
Home treatments can be 70 to 80 percent effective, but must be used consistently. Most home treatments involve acids such as salicylic acid (Compound-W®) that remove the top layers of the wart. Warts are constantly growing so any treatment needs to destroy wart tissue faster than it is growing. 
More recently, home cryotherapy agents such as Compound-W Freeze Off® have become available. These work by freezing the wart tissue and destroying it. In my experience these treatments are not very effective, probably because they don’t provide a deep enough freeze. 
People swear by a number of home remedies including applying pieces of raw garlic cloves or potatoes to the wart when the person is sleeping. Applying duct tape to warts is also rumored to be helpful, but the scientific evidence is weak at best.
Doctors may employ a number of different treatments for warts, but they are not much more effective than home treatments. If the patient has a limited number of warts, freezing with liquid nitrogen can be very effective but painful. There are other acids, chemicals, acne medications and chemotherapy agents that can be applied to warts. Some doctors make their own blend of medications or recommend other home remedies. Sometimes injections are also given in or around the wart to stimulate the immune system to kill the HPV. As a last resort, laser destruction or surgical removal may be used. Any treatment is more effective if it is applied when the warts are small, so don’t wait to get started.
-Dr. John Roberts is a licensed medical physician. He writes a weekly column exclusively for Sagamore News Media publications.