Warts: so common, and so annoying. I see them nearly every day in my practice. At some point, most of us will have one or more, although they are most common among 12–16-year-olds, and affect twice as many White people as those who are Black or Asian.

Warts are a noncancerous growth on the skin. They are not usually painful, and most go away over time, without treatment.

Most common warts are caused by the human papillomavirus (there are more than 100 of them), also known as HPV. Most forms spread through skin-to-skin contact or through shared objects (like towels). The virus enters through breaks in the skin, and while most occur on hands, they can be found anywhere on the body. Once established, they may spread to other body parts and to other people.

Because there are so many types of HPV viruses, warts can look quite different from one another, in shape, size, and color:

• Common warts are typically found on the hands and feel like rough bumps. They may have black dots that look like seeds, but are actually dead capillaries.

• Plantar warts form on the feet, especially the soles. They may be flat or grow inward, and can also have black dots. They can become large and painful to walk on.

• Mosaic warts are white and about the size of the head of a pin. They form on the balls of the feet or under the toes. They are flatter than plantar warts, and don’t usually cause pain when walking.

• Flat warts can develop anywhere on the body, but are usually found on the faces of children. They are small and smooth, and can grow in groups of up to 100.

• Filiform warts look like long threads that stick out. They usually appear on the eyelids, face, or neck.

• Butcher’s warts may develop on the hands of people who handle raw meat, and those who are often exposed to cold and moist environments.

• Genital warts affect the genitals and rectum (anal warts). They are sexually transmitted, and get passed through skin-to-skin contact. They are small, hard nodules and have rough surfaces.

Warts are usually diagnosed visually. They often disappear without treatment, but could take up to two years to completely go away. Typical treatments include over-the-counter medications like Compound W, which is a topical application of salicylic acid. It works 50-70% of the time, but may take months. Your healthcare practitioner can freeze the wart with liquid nitrogen, or burn it with electrodesiccation. Other treatments include immunotherapy, laser surgery, and surgical removal. Note that none of these treatments work perfectly…and the warts may come back!

There is no perfect way to prevent warts. We can lower our risk by avoiding touching any person with known warts, and by not sharing towels, clothing, nail clippers, razors or other personal items. Since HPV enters through cracked or broken skin easily, avoid biting your nails or picking at cuticles, keep skin moisturized, and cover any open cuts. If you have a wart, cover it with a bandage, don’t pick at it, avoid shaving over it, and wash your hands immediately after touching it. Keep your feet dry to prevent the spread of plantar warts.

A few strains of HPV cause sexually transmitted genital warts, and even cancer. Use protection with unknown sexual partners to prevent the spread, and ask your healthcare provider about the HPV vaccine.

Dr. Alan Frischer is former chief of staff and former chief of medicine at Downey Regional Medical Center. Write to him in care of this newspaper at 10927 Downey Ave., Suite C, Downey, CA 90241.