Think about how your palms and soles are positioned in your everyday life, and you’ll realize the difficulty in burning our palms or soles. When you are walking outdoors, the palms are exposed not to the sun, but pressed against your clothing. The soles are covered with socks and shoes. Even if you go to the beach, the palms and soles are likely to get less exposure to the sun than other parts of the body. The palms are usually pressed against the sand when lying down (in our observation, virtually everyone keeps their palms down when lying on their back, and most do when lying on their stomach, too). The soles, even if exposed, are usually kept at an angle to the sun, much less vulnerable than the torso or the face. All things being equal, there aren’t any parts of the unclothed body less likely to burn than the soles or palms.
But all things are not equal, as Worcester, Massachusetts, dermatologist Gerald C. Gladstone explains: “The skin on the palms and soles is much thicker than elsewhere on the body. Approximately 50 percent of the skin’s ability to filter out and protect itself from burning ultraviolet rays is in the outmost tiny fraction of a millimeter of skin, the stratum corneum (the compact outermost portion of the epidermis), which is composed of so-called ‘dead’ skin cells packed together in a tight layer. Because this particular layer is especially thick on the palms and the soles, and in fact is thicker on the heel portion of the sole than anywhere else on the body, its filtering effect for ultraviolet rays is much greater in these locations, so that sunburn rarely develops there.”
Still, burning is possible in the soles and palms. Many skin doctors use ultraviolet A radiation to treat certain diseases, and Samuel T. Seldon, a dermatologist practicing in Chesapeake, Virginia, reports that “this longer wavelength of sunlight can penetrate easily through the thickened skin on palms and soles and burn them quite readily. But most individuals go through their lives without experiencing sunburn on their palms and soles because of the anatomical difficulty of aiming these surfaces toward the sun.”
Lexington, Kentucky, dermatologist Joe Bark adds that even if held in direct sunlight long enough to burn, “the undersides of the wrists would burn painfully long before the palms, thereby inducing someone to escape the sun long before the palmar burning would normally occur.”
Submitted by Dian Watterson of New Orleans, Louisiana