Senior Trends Reporter, HuffPost UK

Serena Williams delighted her fans by playing her first Grand Slam in a year this week – but some people couldn’t help but notice something unusual about her appearance.

Williams, 40, played her first singles match in the opening round of Wimbledon on Tuesday.

While the athlete, who has the most Grand Slam titles of all time, was knocked out by no.115 Harmony Tan, people are still talking about the face tape she had on her right cheek.

The black stickers seemed to make a statement against Wimbledon’s strict all-white dress code, but actually they most likely had a medical purpose.

The tape – known as Kinesio tape (or the brand name KT Tape) – is reportedly being used to help Williams with her sinuses.

In 2007, the tennis ace revealed: “I’m a sinus sufferer. 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 NHS website explains that sinuses are the small empty spaces behind your cheekbones and forehead that connect to the inside of the nose. If they get infected, you can develop sinusitis.

The NHS describes sinusitis as a “swelling of the sinuses, usually caused by an infection” which prevents mucus draining into your nose and throat properly, making you feel blocked up.

It’s a common infection, and can usually go away without medical treatment.

Pain, swelling and tenderness around cheeks, eyes or forehead

A reduced sense of smell

A green or yellow mucus from your nose

Mild sinusitis can clear up within two to three weeks, if you get plenty of rest, drink a lot of fluids, taking painkillers, avoid allergic triggers and smoking, and clean your nose with a salt water solution to ease congestion.

Pharmacists could recommend decongestant nasal sprays or drops, salt water nasal sprays or solutions to rinse out the inside of your nose.

But if symptoms are severe, do not improve after a week or keep coming back, should you go to your GP.

They may be able to provide steroid nasal sprays or drops, antihistamines, antibiotics or in some cases, surgery.

According to KT Tape’s website, the elastic tape is designed to provide “drug-free pain relief and flexible support to help keep you and your muscles active and recovering”.

It adds: “KT Tape creates neuromuscular feedback (called proprioception) that inhibits (relaxes) or facilitates stronger firing of muscles and tendons.”

The website does list all the potential places you could put this tape, and pointedly does not suggest putting it on your face.

After cross-country skiers were seen wearing the tape on their faces to protect themselves from the cold in Beijing, the company’s CEO warned it could get stuck.

Greg Venner said: “KT Tape doesn’t endorse the use of kinesiology tape on the face as it isn’t clinically tested. And the adhesive that works so well to keep the tape in place to provide long-lasting muscle and joint support can be a bit more difficult to remove from the delicate skin on the face.”

However, he added: “We certainly applaud the creativity.”

Billie Eilish was also seen sporting the tape during her Glastonbury set last week, although she had it on her knees and shins.

Senior Trends Reporter, HuffPost UK