Smearing sunscreen over every square inch of skin is a tedious but necessary task to guard against the sun’s damaging rays. But it can be a challenge to keep re-applying it, particularly while sightseeing and socializing. On the other hand, sun-protective clothing can be donned at the last minute for added sun protection throughout the day.

UPF vs. SPF Ratings

Sunblock and sunscreen are rated by sun protection factor (SPF) and textiles are rated by ultraviolet protection factor (UPF), both of which measure the transmittance of UVB rays (the ultraviolet rays that burn the skin), and UVA rays (the ultraviolet rays that tan, wrinkle, and prematurely age skin). According to the American Society for Testing and Materials (ASTM), a UPF rating of at least 15 is required for a garment to be classed as solar UV-protective. The higher the protective factor, the higher the UPF rating.

Robin Ashinoff, MD, director of dermatologic and mohs surgery at Hackensack University Medical Center in New Jersey, says sun protection should be top-of-mind for everyone, especially people with arthritis who are on long-term immunosuppressive drug therapy, such as methotrexate or cyclosporineause. She says, “These drugs have been shown to increase light sensitivity and raise the risk for skin cancer. And for people living in the South, who tend to spend more time outdoors, the lengthier time of exposure to the sun is of particular concern.”

Selection Guidelines

Some sun-protective fabrics are pretreated with UV-absorbing compounds, such as titanium dioxide. However, it’s the total design of a garment, not just the fabric that is important in gauging the sun safety of what you wear. According to Kathryn L. Hatch, PhD, a University of Arizona professor who has extensively researched the topic, sun-protective value is based on a combination of fiber, weave, color and weight. You can use these factors to gauge the potential UV-protection of apparel labeled as sun-protective – or what’s hanging in your closet now.

Fiber: Nylon and polyester have high UV absorbance. Cotton and rayon are the least UV-absorbing fibers. Laundering the latter with Rit Sun Guard or a brightening agent can put these clothes in the UPF 30+ category.

Weave: In general, thicker, tightly-woven fabrics with dense fibers, as in denim and leather, keep rays from seeping through your clothes. However, repeated washing of loosely woven fabrics tightens the fibers, enhancing sun protection. Similarly, laundering with heavy-duty detergents that contain optical whitening agents on garments increases UV absorption. Watch out for fabrics that stretch, as stretching opens spaces between the threads to let the sun in.
 
Colors: Dark colors such as brown, black, navy and forest green potentially absorb more UV rays than light colors and pastels. However, the type of dye used varies, such that even lighter-colored garments may have been treated with a darkly pigmented dye.