People infected with coronavirus may end up developing a chilblain-like inflammation on their feet that could cause their toes to turn a purple colour, scientists have said.
Research by the International League of Dermatological Societies and the American Academy of Dermatology found some patients had a symptom known as Covid toes.
The condition typically develops within a week to four weeks of being infected and can result in patients' toes becoming swollen or changing colour, sometimes lasting for months at a time.
Covid toes is said to mostly cause mild symptoms with patients' feet returning to normal within weeks for the majority of cases.
Scientists also discovered that about one in six people require hospital treatment, while some of those with “long Covid” symptoms report cases lasting for several months.
“It seems there is a certain sub-group of patients that, when they get Covid, they develop inflammation in their toes, which turns them red and swollen, and then they eventually turn purple," said Dr Esther Freeman, principal investigator of the International Covid-19 Dermatology Registry, the collaboration between the two research bodies.
“In most cases, it is self-resolved and it goes away. It is relatively mild.
“It lasts on average about 15 days. But we have seen patients lasting a month or two months.”
She told the PA news agency: “What is very surprising is when you get beyond that 60-day mark – because it’s not like patients are resolving at day 70.
“It’s the fact that some of our patients are at over 150 days now – these are patients with red or purple or swollen toes for many months.”
About half of the patients in the registry are reported to have Covid toes and about 16 per cent of those had to be hospitalised as a result, the figures suggest.
Dr Freeman said the identification of people with Covid toes symptoms – including some in the UK – helps scientists understand more about coronavirus related symptoms elsewhere in the body.
She said: “We are starting to see long Covid in other organ systems, this is the first time we are recognising this can happen in the skin as well.
“I think it raises a lot of questions about what sort of inflammation is going on – is there inflammation elsewhere in the body? We don’t really know the answer yet.
“The skin can be viewed as a window into the rest of the body because it is inflammation which you can see – and can be indicative of inflammation elsewhere.”
The figures are submitted by doctors treating patients with skin issues in dozens of countries around the world, meaning there are potentially many people with Covid toes who have not sought medical help.
Dr Freeman said: “I think what we’re reporting is probably just the tip of the iceberg – it’s probably happening a lot more than we’re reporting but I think by reporting it more people will recognise it.”
The figures are being presented at the European Academy of Dermatology and Venereology (EADV) Congress in Switzerland this week.
Additional reporting by PA Media.