Update 18 June:the Health and Safety Executive has notified us that Under Armour has withdrawn the face covering from sale in the UK, so it intends to take no further action. The face covering may still be available through third party retailers, though.
Under Armour's Sportsmask has been withdrawn from sale in the UK and Europe due to concerns raised about a chemical in the material - but the company maintains the product was safe to use.
Marketed as a face covering for exercising, the Sportsmask has been a popular product since its launch last year.
The alert warns that 'PHMB is harmful if inhaled and may cause an allergic skin reaction. By inhalation, it causes damage to organs through repeated exposure and is also suspected of causing cancer.'
PHMB is a preservative and antimicrobial agent and its use was restricted under EU regulations in 2016 - which still apply in the UK.
The mask is on sale at multiple outlets in the UK, including Sports Direct, House of Fraser and Wiggle, but Under Armour has stopped selling the mask on its own website while it investigates the safety alert.
Under Armour told us:
The Sportsmask has not been recalled from customers, and is still on sale in the UK.
The EU has strict regulations concerning biocidal products, and any serious or long-term risk from tiny quantities of PHMB is thought to build up over time, so don't panic if you've been using this mask for a few months. Although PHMB is listed in EU regulations as a suspected carcinogen, more evidence is needed to prove a link.
Under Armour told us that it stands by the mask being safe, because of how PHMB is applied to the mask.
The level of PHMB allowed - if at all - differs depending on the type of product, so this seems to be a dispute about whether Under Armour is on the right side of these regulations.
We've notified the Health and Safety Executive, which regulates biocidal products in the UK. It told us:
'This active substance has been approved for product-type 2 use (i.e. disinfectants and algaecides not intended for direct application to humans or animals) and so can be used in product-type 2 biocidal products that have been authorised, as well as for the purpose of producing 'treated articles'.'
We are seeking information on which category this product falls into, but the HSE also confirmed that the product has been removed from sale in the UK by Under Armour.
Unfortunately, if you own one of these masks, the situation isn't very clear cut right now. If you are concerned, then you could use an alternative mask until more information comes to light.
Under Armour also told us a newer version of the mask will soon be coming out which doesn't have PHMB in it 'in order to comply with differing global rules'.
We'll update this page once we know more.
There's been a rise in face coverings with antimicrobial properties (which inhibit growth of germs) for sale, as manufacturers try to innovate in this new and fast-moving market.
While there is emerging evidence to support some of these claims, we still don't know exactly how well most of these products work at inactivating viruses like Covid.
There are also some safety concerns with the sudden widespread use of antimicrobial fabrics in something that we use on our faces and in close proximity to our airways.
In Denmark, the national standards for face coverings actually bans those with antimicrobial treatment.
Our colleagues at the Danish consumer organisation, Forbrugerru00e5det Tu00e6nk, told us 'the active substances may be problematic, and the claims are often misleading.'
In Canada, health authorities have advised people not to wear masks containing graphene - another antimicrobial agent - while potential health risks are investigated.
Some antimicrobial face coverings adhere to independent standards, like the Oeko-Tex Standard 100, which certifies that the material has been tested and deemed harmless to human health.
You can look for the Oeko-Tex Standard 100 badge on product packaging. But it's also worth being aware that previous reports have found , so be wary of where and who you buy from and don't take anything at face value.