Q: I have genital warts, both on the penis and anus. What treatments are available?

A: Warts are caused by infection with human papillomavirus (HPV). There are many different strains of papillomavirus. Most warts do not cause cancer, but certain strains of papillomaviruses can cause warts with a moderate risk of becoming cancer.

HPV can spread on the body and can be transmitted to others. Sexual contact is the most usual way that genital warts are spread.

You may have seen over-the-counter treatments with salicylic acid that are often used to treat warts on the hands or feet. These should NOT be used in the genital area.

For treatment of warts on the penis, anus, or in other genital areas, your doctor can prescribe topical creams. One example is imiquimod (Aldara), which helps your body fight off the wart. Other options include podofilox or 5-fluorouracil (Efudex) that directly attack wart cells.

Irritation from these topical treatments is common, so it's important to carefully follow your doctor's instructions.

Warts can be resilient. You may need several treatments to get rid of them. Even if they appear to have been removed, warts can come back at a later time. To treat persistent warts, your doctor may choose to laser, freeze, or remove them with a scalpel.

If a wart is suspicious for cancer, your doctor will do a biopsy to surgically remove part of the wart. The specimen is sent to a pathology laboratory for evaluation.

For all of these reasons, it's important to see your doctor for treatments of warts on the penis, anus, or other genital areas.

Rebecca Campen, M.D., J.D., is an assistant professor of dermatology at Harvard Medical School. She divides her time between clinical practice of dermatology at the Massachusetts General Hospital and private practice in Savannah, Ga.

(For additional consumer health information, please visit http://www.health.harvard.edu.)