Serena Williams was using KT Tape on her face at Wimbledon to help her sinuses

• On Tuesday, Serena Williams returned to Grand Slam tennis for the first time in a year at Wimbledon.
• Williams was seen wearing special tape on her right cheek in an eventual loss to Harmony Tan in three sets.

Serena Williams excited the sports world on Tuesday with her return to Grand Slam tennis, but she looked a little different at the All England Club.

Williams played her first singles match in a year during the opening round of Wimbledon, against No. 115 Harmony Tan. And while the powerful tennis looked familiar, Williams committed too many unforced errors (54 to Tan's 28) and appeared fatigued as the match stretched on — and on. Over three hours and 11 minutes, Williams and Tan went back and forth in an instant classic that ultimately came down to a third-set tiebreak, which the Frenchwoman Tan won, 10-7.

During the match, Williams created a small buzz as she was seen sporting black "stickers" on her face.

According to the UK Times, those stickers are actually Kinesio tape, also known as kinesiology tape or its brand name, KT Tape, and Williams has said she is using them to help her sinuses.

She uses the tape in hopes that it will prevent pain and ease pressure in and around her nose.

"I'm a sinus sufferer," Williams said in 2007. "Playing tennis or pretty much doing anything every day is not easy when you have sinuses. You feel a lot of pressure, congestion, and pain, and training for Grand Slams ... it's not easy."

The tape was made famous by Olympic athletes, especially in beach volleyball.

According to KT Tape's website, "KT Tape is designed to provide drug-free pain relief and flexible support to help keep you and your muscles active and recovering." They add: "KT Tape creates neuromuscular feedback (called proprioception) that inhibits (relaxes) or facilitates stronger firing of muscles and tendons."

Kevin Loria of Business Insider wrote that the lists of conditions the tape is said to help include headaches, sore muscles, and shin splints. Other conditions include runner's knee, shoulder pain, back pain, and even plantar fasciitis. It is believed that when applied properly, the elasticity of the tape helps gently lift the skin from the tissue underneath, thereby relieving pressure and easing pain.

However, Loria noted that as of 2016 there was limited research to back up the claims. He did find several reviews that said the tape could help pain relief and may increase the range of motion slightly.

While the tape is typically used to prevent or help recover from muscle injuries, some athletes, like Williams, have found off-label uses for the product.

During the Winter Olympics earlier this year, cross-country skiers were seen wearing the tape on their faces to help protect their skin from the cold temperatures in Beijing. At the time, KT Tape's CEO warned that it could get stuck to their faces but noted that he liked the "ingenuity."