Weight: Heavier is better, as it has more mass to repel sun seepage. The downside  – insulated fabrics collect heat and make you perspire. Some sun-protective shirts and pants have built-in, webbed mesh panels along the side or under the forearm for ventilation and breathability. 

Wetness: Fabrics of 100 percent cotton that are white or pastel have been shown to lose UPF when wet. One study showed a 1/3 reduction in SPF when both a synthetic surf shirt and cotton-polyester T-shirt were wet. Still, fabrics with UV absorbers or certain dyestuff compounds are designed to retain sun protection performance when wet. And some swimsuits are made of fabrics treated to resist the effects of chlorinated water on UV-protective levels.

Ashinoff advises patients to use sunblock under clothing – regardless of what you wear. “People don’t generally wear special sun-protective clothing, just because it’s expensive. So choose the highest SPF sunblock you can, wear a hat, get into the shade – and don’t go running at 12 noon.” Sunblock provides better sun protection than sunscreen, which is typically more transparent when applied to the skin and can break down faster once exposed to the sun.

Shield the Sun Stylishly

Head-to-toe sun protection is promoted by an array of specialty clothing companies. Here are a few:

Sun Precautions: Rating: 30+ SP.

Coolibar: Rating: UPF 50+.

Columbia: Rating: UPF15 to 50 (Omni-Shade).

Nozone: Rating: UPF 50+.