As many continue enjoy long sunny beach days, finding ways to stay safe from extreme sun exposure is top-of-mind.
One TikToker, who takes UV protection seriously, recently shared a warning to others about SPF — or lack thereof — in white clothing.
"I've had like multiple skin scares... so I don't f— around when it comes to the sun," the woman, identified on the app as Liz Fox Roseberry, said in the video.
She then described her usual summer outfit as shorts, a tank top, a bandana around her neck, and a long-sleeve shirt as a cover-up. Despite wearing that every day, she was still getting sunburns on her shoulders, she claimed.
Then, Roseberry said her husband blew her mind with a little-known fact.
"He said white shirts don't protect you from the sun. And I'm like 'what?'"
To find out what kind of sun protection clothes really offer, Yahoo Canada checked in with a Toronto dermatologist.
Do clothes protect you from sun exposure? Expert weighs in
Dr. Benjamin Barankin, medical director and founder of the Toronto Dermatology Centre, said breathable fabrics and clothing are "a good way to protect from sun exposure."
However, some fabrics are better at it than others. That's measured by UPF — the same as SPF, but used exclusively for clothing.
According to the Skin Cancer Foundation, UPF (Ultraviolet Protection Factor) indicates how much UV radiation a fabric allows to reach the skin.
"For example, a UPF 50 fabric blocks 98 per cent of the sun’s rays and allows two percent (1/50th) to penetrate, thus reducing your exposure risk significantly," the agency explained.
The foundation said a UPF of 30 to 49 offers very good protection and anything over UPF 50 is excellent. That protection depends on the colour, content and fit of the fabric.
Dr. Barankin said, "white clothing, like a t-shirt, provides approximately UPF of 7, and if it's wet, it goes down to a 3," Barankin said.
Though it's a low number, Barankin said a UPF of 7 "is okay" when out for up to two hours. Otherwise, people should consider wearing at least SPF 30 sunscreen under light-coloured shirts.
"Same with a [beach] cover-up, although if you double it up, then there is increased protection," the dermatologist said.
What fabrics are most and least protective?
According to Barankin, "denser weaves are more protective than looser weaves," when it comes to fabric.
A dark pair of jeans or a denim shirt, for example, can provide UPF of up to 1,700.
"Darker clothing is more protective because it absorbs more UV than lighter colours. The more vivid the colour, the greater the protection," the doctor said.
Unbleached cotton contains natural lignins that act as UV absorbers, Barankin added. However, generally polyester and nylon offer "offer more sun protection than natural fibres."
"Shiny polyesters and even lightweight satiny silks can be highly protective because they reflect radiation."
Some high-tech fabrics can also be treated with chemical UV absorbers or dyes to prevent some penetration from UV rays, he explained.
There is one way to tell whether there's protection from the sun, according to Barankin.
"If you lift up the clothing to the sun and can see through the clothing or hat, then UV rays are penetrating through as well."Dr. Benjamin Barankin
Wool and silk are moderately effective, the expert said, while cotton, rayon, flax and hemp are the least effective, unless specific UPF treatments are added.
"As a fabric becomes more worn or fades, it becomes less effective at blocking UV light. Stretched fabric can lose a significant amount of its UPF."
Shrinkage from doing laundry, however, actually results in a tighter weave and increased UPF.
How to ensure you're well protected?
Barankin said the best option to stay safe from extreme sun is a combination of hat, sunglasses and lightweight darker clothing if possible.
But, it's also important to wear sunscreen and avoid mid-day sun.
"Do your outdoor exercise early in morning (e.g. before 9 a.m.) or late in evening," Barankin added.
"If it’s smoky outdoors, or high pollution, or UV index, simply skip that day for outdoor activities," he advised.
"Remember that sun protection isn’t just for sunny days, and drink plenty of water!"