A leading scientist has warned of a new symptom that would show if you have already had coronavirus.

Professor Tim Spector has said that people may notice changes to their fingernails after a Covid infection.

Professor Spector, who is the principal investigator of the Zoe Covid Symptom Study app, said that the difference can happen even if you did not experience any other symptoms of Covid-19. 

Here’s what you need to know:

What do ‘Covid nails’ look like?

Professor Spector noted that people who have a "clear line", which creates a prominent ridge, growing out of the nail may have had Covid before.

People may also notice discoloration under their nails if they have previously had the virus.

The professor said it is recognised as the nails recover after an infection. However, he adds that these are usually harmless and can be caused by any illness - meaning it is not only linked to Covid-19.

Writing on Twitter, Prof Spector said: "Do your nails look odd? COVID nails are increasingly being recognised as the nails recover after infection and the growth recovers leaving a clear line. Can occur without skin rashes and appears harmless."

Several Twitter users responded to the post stating they had experienced this symptom after being unwell.

Julie McGlue replied: "Myself & my husband had covid last September & we noticed we had grooves in our nails too"

User pippabrunton said: "I noticed this and also hair loss 3 months after covid"

Drizzydre00 wrote: "Ok but I 100% had nails that looked like this in March 2020 and that’s cause everyone in the show I was in in February 2020 probably had Covid but it was before testing was a common thing but this is more proof that we actually did have it!!!!!!!!!!!"


Why do the ridges appear?

These horizontal grooves appear on the nail after an infection and are known as Beau’s lines.

The lines are commonly found in patients who have had a viral illness. This is due to the stress that their body was under battling the virus.

These have been reported among people who have experienced Covid toes or fingers when the skin has become discoloured.

The lines will eventually grow out over time.

Dr Tanya Bleiker, president of the British Association of Dermatologists, explained: "Dermatologists are seeing 'Covid Nails' in some patients who have had an infection with SARS-CoV-2, the virus responsible for Covid 19.

These changes have long been recognised as 'Beau's lines' and are transverse indents in the nail of many, or all, fingernails and sometimes toenails.

"They are caused by a temporary interruption of the growth of the nail due to a number of causes including febrile illnesses such as Covid-19 infection.

"These indents tend to appear two to three weeks after the illness - longer in toenails.

"They are harmless and grow out with time - often surprisingly a few months."