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People are seen at Jones Beach, in Wantagh, N.Y., on May 28, 2016.Julie Jacobson/The Associated Press

The ultimate in sun safety is UV-protective clothing, according to the Canadian Cancer Society.

Skin-cancer specialists agree. "Clothing is always going to work better than sunscreen because it blocks both UVA and UVB rays," said Dr. Douglas Grossman, an expert in skin cancer at Huntsman Cancer Institute in Utah. And unlike sunscreens, which we tend to use too sparingly, "it's not going to wash off."

Sun-safe clothing has come a long way since the scratchy garments introduced in the 1990s. Back then, "they looked like prison uniforms," said Dr. David Leffell, a professor of dermatology at Yale University. "No one would wear them."

Manufacturers used to rely on tight weaves to block out the sun's rays, said Dr. Michael Huether, a skin-cancer surgeon in Tucson, Ariz. But even with vents to prevent wearers from overheating, the clothing felt "like an old army tent," he said.

Today's sun-protective sportswear is more breathable, lightweight and stylish. Garment makers use specific fabrics and a combination of special dyes, minerals or chemical treatments to increase an item's ultraviolet-protection factor, or UPF.

How they work

UPF measures blockage of both UVA and UVB rays, whereas the sun-protection factor (SPF) in sunscreens only measures the filtering of UVB rays. UVB is the kind that causes sunburn and skin cancer, but UVA penetrates deeper into the skin, causing skin cancer as well as premature aging.

A standard white T-shirt has a UPF of about 7, while the best sun-protective clothing has a UPF of 50-plus. That means the fabric should block 98 per cent of the sun's radiation from reaching the skin.

Synthetic fabrics such as polyester, which has light-absorbing benzene rings within the polymer, tend to block more UV radiation than natural fibres such as cotton.

How they're made

Many manufacturers add special dyes that contain molecules that disrupt UV radiation. While garments with higher concentrations of these dyes tend to be darker, dye colour is not the only factor in blocking UV rays, said Huether, who learned the ins and outs of sun-protective fabrics while developing a clothing line called Uvida Sportswear.

Brands such as Coolibar from Australia include UV-blocking minerals such as zinc oxide and titanium dioxide, which are woven into the fabric. These are the same minerals found in sunscreens that protect against both UVA and UVB.

Other manufacturers treat fabrics with chemicals such as Tinosorb FD, the trade name for a family of UV-absorbing chemicals. Tinosorb is also the active ingredient in Rit Sun Guard Laundry Treatment, a detergent that consumers can use to increase the SPF of normal clothing at home.

The detergent can raise the UPF of everyday cotton up to about 30, for up to 20 washings, according to the New York-based Skin Cancer Foundation, which recommends the product.

Safety data on Tinosorb FD indicate that it irritated the skin and eyes in rodents exposed to large doses of the raw chemical. But Tinosorb FD has been shown to bond tightly to fabric fibres. Australian regulators concluded that potential human exposure to the chemical from fabrics would be low.

Safety concerns?

Dermatologists such as Huether and Leffell expressed no concerns about sunscreen chemicals in UPF garments. Nevertheless, the Environmental Working Group, a non-profit research organization based in Washington, recommends against using chemically treated clothing. "You can protect yourself and your family without these chemical additives," the group's website states.

Some companies, such as grUVywear and SunBusters, market their garments as chemical-free. But other manufacturers do not necessarily disclose whether their fabrics are infused with chemical sunscreens.

Similarly, consumers have little way of knowing whether garments live up to their sun-protection claims. In general, UPF ratings are based on standards and testing methods developed by industry groups including ASTM International (formerly the American Society for Testing and Materials). Better manufacturers subject their fabrics to a UV transmittance test, followed by a second test after multiple launderings and exposure to simulated sunlight.

But these are voluntary measures. Although the U.S. Federal Trade Commission monitors UPF advertising claims, testing of these products is up to individual manufacturers. "There's no real certification label that you can look for," Huether said.

The bottom line

Huether recommends that consumers search for information on manufacturers' websites, and stick with the brand names they trust. Most clothing with a UPF rating of 50-plus should provide adequate protection, he said. And at the end of the day, he pointed out, the best sun-safe clothing "is the one that you'll wear."

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