Fibers in yoga clothes can cause burns during MRIs: What to know

High-tech athletic clothes made with anti-odor fabrics are popular. But they also come with a little-known health hazard: The apparel may be infused with metal fibers that can cause burns in an MRI.

“It’s like putting your skin up against a hot plate,” said Dr. Hollis Potter, chairman of the radiology and imaging department at the Hospital for Special Surgery in New York City.

Lululemon, one of the largest athletic apparel brands, boasts on its website that its “Silverescent” technology infuses silver fibers into fabric to make it “stink-stopping.” But the company declined to discuss which of its clothes may contain metal fiber. The company also did not comment on the risk of wearing Silverescent clothes during an MRI, which stands for magnetic resonance imaging.

“With any medical care, patients should check with their doctor to understand pre-treatment policies,” a Lululemon spokeswoman said.

But warnings about the risk are happening on social media accounts and in some in some MRI scanning centers as doctors, radiology technicians and patients warn that certain high-tech stretchy workout clothes can pose a burn risk when getting an MRI.

In March, Danielle Squires, 29, of Nova Scotia, said she was getting a shoulder MRI scan following a car accident. Squires said she was already in the machine when the MRI technician stopped and noticed her Lululemon leggings.

“I had to take them off because she said there might be metal in them,” said Squires, who also shared her story on TikTok. “I had no idea.”

In a statement, Lululemon said its leggings sold today are not made with Silverescent fabric, but the company declined to comment on whether leggings sold in the past contained the fibers.

On the resale site Poshmark, two users say they are selling Lululemon “Wunder Under” leggings made with Silverescent fabric.

On the Lululemon website, the company sells tennis skirts, T-shirts, tank tops and headbands made with Silverescent fabric.

Patients who get MRI scans are advised to remove jewelry and any metal from their bodies, and they are sometimes even checked with metal detectors to make sure nothing metallic accidentally enters the machines.

But depending on the reason for the scan, patients may be allowed to leave on yoga pants, socks and other clothes during the procedure. MRI experts say that many patients and technicians aren’t aware that some stretchy athletic clothes, as well as masks and blankets, can contain metal fibers that aren’t picked up by metal detectors.

MRI machines use powerful magnets and radio waves to produce images of your tissues, organs and skeletal system. Wearing clothing with even trace amounts of metal can interact with the magnetic field and burn skin.

As of December 2020, there have been at least six published case reports involving burns from textiles, but experts suspect many more have gone unreported.

The first reported case involved an 11-year-old girl who endured a second-degree burn while sedated during an MRI. The contents of the girl’s undershirt, sold by Boston Orthotics & Prosthetics, were identified only as “Coolmax/Lycra.” It was later found that the shirt contained silver-embedded microfibers. The girl’s burns corresponded with the seams of the shirt, where the silver was concentrated.

Thomas Morrissey, president and CEO of the company that sold the shirt, said the firm learned about the incident five years after it was published as a case report. A warning on the Boston Orthotics & Prosthetics website and a sticker on the packaging states that the shirt should be removed before an MRI.

Jeffrey Rogg, the MRI medical director at Rhode Island Hospital who was involved in the case, said it played a critical role in raising awareness about metallic fibers: “It became evident to the community that metallic fibers aren’t necessarily going to be visible or detectable.”

Another case in 2019 involved a 40-year-old woman in Japan who sustained second-degree burns from jogging pants that were labeled as 100 percent polyester but apparently contained metallic fibers. Another patient suffered third-degree burns around their face and neck while wearing a mask containing metallic fibers, prompting an FDA warning in 2020.

Injuries sustained during an MRI are rare, but data shows that thermal burns are the most common, and that in about 5 percent of those cases, the burns are caused by patient clothing.

Today, you can find silver in a range of clothing, products and fabrics, including air filters, food packaging, medical devices, socks, bedsheets, underwear and even face masks. In addition to Lululemon’s Silverescent fabrics, Gap’s Athleta sells clothes with Ionic+ silver-infused fabric, and Patagonia sells HeiQ Pure odor-control clothing made with “silver-salt based” additives.

Athleta and Patagonia didn’t respond to requests for comment.

But many people associate the metal-infused fabric with Lululemon, which has promoted its Silverescent technology as a way to conquer smelly workout clothes. The technology used in the fabric “bonds 99.9 percent pure silver to the surface of every fibre — which means that there’s stink-conquering technology woven into the very fabric of your favorite workout clothes,” according to the company’s website.

Silver has anti-bacterial properties and can penetrate bacterial cell walls. The positive ions in silver are attracted to negative ions in bacteria, ultimately resulting in the death of the microbe, said Bryan James, a researcher at the Woods Hole Oceanographic Institution who specializes in materials science.

Noble Biomaterials, which supplies Lululemon, the Gap’s Athleta brand and other athletic gear makers, said in an email that it was “passing” on commenting about the issue, but that it concurs with recommendations that patients wear gowns in MRI machines. “All fabric is unsafe” to wear in an MRI machine “unless proven otherwise,” the statement said.

Lululemon declined to answer questions about whether it has warned consumers about the risk of Silverescent fabrics and MRI scans.

“If your readers would like to determine if Silverescent technology is used in a product, information on our products can be found on our product hang tag, clothing care label and in the product features section on our website and app,” the company said in a statement through their public relations firm, Edelman.

Experts say you can’t always rely on clothing labels to tell you that a fabric contains metal fibers. Although the Federal Trade Commission requires that all clothing labels list materials used in a fabric, the rule doesn’t apply to fibers that make up 5 percent or less of the fiber content.

Even trace amounts of metallic fibers can burn someone, said Michael Hoff, member of the American College of Radiology MR safety committee and director of diagnostic medical physics at the University of California at San Francisco.

“Most places are on top of this and gowning patients anyway,” Hoff said. “But it’s something we should be concerned about because it can cause distress to the patient, and preventable risks should be avoided at all costs.”

Potter said that MRIs aren’t supposed to be painful, so anyone who feels discomfort during a scan should alert medical staff right away.

Some MRI facilities may not ask you to fully gown up, either because technicians aren’t aware of the potential risks metallic fibers pose or they aren’t convinced the risk is serious enough, Potter said. In those cases, take your safety into your own hands and request a gown to change into.

“MR is an amazing diagnostic tool, but we have to respect the science and technology behind it,”Potter said.

To lower risk, avoid wearing clothes that say “antimicrobial” or “antibacterial,” experts say, because they may include metallic fibers. The safest bet is to disrobe completely and wear the gown provided by the MRI technician.

Chaundria Singleton, an MRI technician in Atlanta, has used TikTok to spread word of the risk. She said that whether the patient is wearing Lululemon or another brand, she always asks patients to remove their clothes and put a gown on.

“We don’t want to waste your time and make you uncomfortable to change into our gowns,” Singleton said. “We just want to make sure you’re safe, and you get this test done without it harming you.”

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Fibers in yoga clothes can cause burns during MRIs: What to know