A face mask worn by celebrities, Instagram influencers and fashion week attendees costing between NZ$100 and $475 has sold out, after high-profile customer Gwyneth Paltrow told fans to "stay safe" amid the coronavirus pandemic.
But the World Health Organisation advises the only people who need to be wearing masks are those coughing and sneezing or healthy people who are taking care of a person with suspected COVID-19 infection.
"If you do have a cough, fever and difficulty breathing, you should wear a mask and seek medical care," WHO infection prevention and control consultant Christine Francis said.
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"If you do not have these symptoms, you do not have to wear a mask because there is no evidence that they protect people who are not sick."
Paltrow shared a snap of herself on a plane to Paris two weeks ago wearing a black air mask by Airinum. All the Swedish brand's products are sold out.
"Paranoid? Prudent? Panicked? Placid? Pandemic? Propaganda? Paltrow's just going to go ahead and sleep with this thing on the plane," she wrote.
"I've already been in this movie. Stay safe. Don't shake hands. Wash hands frequently."
Paltrow starred in the 2011 film Contagion, about a worldwide deadly virus pandemic, carrying the tagline "Nothing Spreads Like Fear".
Fans of the actor and Goop lifestyle brand founder have a history of following her lead.
Airinum's Urban Air Mask 2.0, marketed as "the world's most advanced mask", sells for just over NZ$ and is available in onyx black, quartz grey and pearl pink.
The NZ$475 version was produced in collaboration with Italian fashion brand Nemen and is sold in pistachio green, military green and a limited-edition grey print with Norwegian music producer Alan Walker's logo.
Pictures have also emerged on social media of black or black-and-red masks by Airinum in collaboration with French fashion designer Marine Serre, selling for NZ$475. They have also been spotted at fashion week in London and Paris, held in the past month.
"With face masks becoming an accessory for the 21st century, we wanted to bring our air masks into the fashion industry, in an attempt to rethink and challenge norms and to hopefully spark a debate and raise awareness about climate change," Airinum states on its website.
It claims the air masks are for protection from "all types of airborne particles" including pollution, smog and pollens and also reduce "exposure to bacteria".
But the description is followed by a note that they are "not certified for clinical environments such as hospitals or allied health clinics".
"Wearing the mask cannot fully remove risk of infection, as this will depend on other factors including fit and application," the brand, founded in 2015, states.
Despite this, Airinum has seen a surge in mask-wearers as a result of the coronavirus pandemic and has lengthy waiting lists.
"We are currently out of stock on all products and we are working hard to get new ones as soon as possible," the website states.
"At the moment we estimate to have a limited amount of masks available in April and a large amount of masks and filters available in July. We apologise for this inconvenience."
The WHO, on its coronavirus public advice page, states masks are only effective "when used in combination with frequent hand cleaning with alcohol-based hand rub or soap and water".
"If you wear a mask, then you must know how to use it and dispose of it properly," it reads.
"Replace the mask with a new one as soon as it is damp and do not re-use single-use masks."
This morning, Airinum posted an update to customers about washing the Urban Air Mask 2.0.
Paltrow wasn't the only celebrity to share a mask selfie to Instagram in late February.
Actor Kate Hudson and model Bella Hadid, who have 11 million and 29 million followers respectively, both recently snapped themselves travelling with surgical masks on their face.
In the days after the celebrity posts, US Surgeon General Jerome Adams urged people to "STOP BUYING MASKS!".
The Australian government this month addressed the use of surgical masks during the coronavirus outbreak.
"Surgical masks in the community are only helpful in preventing people who have coronavirus," the health department said.
"If you are well, you do not need to wear a surgical mask as there is little evidence supporting the widespread use of surgical masks in healthy people to prevent transmission in public."
Health Minister Greg Hunt on Sunday announced the government had secured an additional 54 million face masks to help protect "frontline workers" such as medical and aged care professionals looking after suspected or confirmed coronavirus cases.
"If you are suspected of having coronavirus disease, your primary care provider will give you a surgical mask to wear when you enter the emergency department or general practice," the health department states.