Flat warts are small, smooth, painless growths that can arise anywhere on the body, though they are most commonly seen in groupings on the face and hands. Like all warts, they are caused by a human papillomavirus (HPV) infection. Flat warts are frequently seen in young children, yet they rarely manifest after adolescence. They are almost always harmless and only persist for a few years, though some people choose to have them removed for aesthetic purposes.
Researchers have discovered hundreds of different strands of HPV that can manifest in any number of ways. A few specific strands, namely HPV types 3, 10, and 28, are associated with the development of flat warts. These types only rarely become malignant or cause other kinds of warts to appear. The likely reason why children are affected more commonly than adults is that developing immune systems are less effective at suppressing HPV infections.
A typical flat wart is less than 0.2 inches (about five millimeters) in diameter, slightly raised, and lighter in color than surrounding skin. It is common for warts to appear in clusters, with dozens or hundreds of individual spots grouped closely together. Most cases are isolated to a cheek, underneath an eye, or on the forehead. Clusters of flat warts appear less commonly on the backs of the hands, the shins, and the tops of the feet.
Flat warts are normally are benign, though they should still be inspected by a doctor to rule out the possibility of a more serious skin condition. A dermatologist can inspect the warts and collect a tiny sample of skin for laboratory analysis to confirm the presence of an active HPV infection. After making a diagnosis, the doctor can explain the physiology of the condition and discuss treatment options with parents and the patient.
Dermatologists do not usually suggest aggressive treatment for flat warts, pointing out the fact that they are not a reason for concern and will likely go away on their own within about two years. If parents want to decrease healing time, they may be instructed to try an over-the-counter topical cream containing salicylic acid to irritate and erode the affected skin. A high-strength ointment containing retinoic acid may be prescribed for persistent or recurring warts. Cryotherapy and surgical removal are options for many kinds of warts, but doctors generally discourage such measures for flat warts, especially if they are on the face. Scarring from surgical treatment would persist for much longer than the warts themselves.