KCL study suggests skin rash should be considered the fourth key symptom of COVID-19

A new pre-print study led by King’s College London has found that characteristic skin rashes and ‘COVID fingers and toes’ can occur in the absence of any other symptoms and therefore should be considered as key diagnostic signs of the virus.

Using data from the COVID Symptom Study app from around 336,000 regular UK users, researchers discovered that 8.8% of people reporting a positive coronavirus swab test had experienced a skin rash as part of their symptoms, compared with 5.4% of people with a negative test result. Similar results were seen in a further 8.2% of users with a rash who did not have a coronavirus test, but still reported classic COVID-19 symptoms, such as cough, fever or anosmia (loss of smell).

To investigate further, the team set up a separate online survey, gathering images and information from nearly 12,000 people with skin rashes and suspected or confirmed COVID-19. The team particularly sought images from people of colour, who are currently underrepresented in dermatology resources.

17% of respondents testing positive for coronavirus reported a rash as the first symptom of the disease. And for one in five people (21%) who reported a rash and were confirmed as being infected with coronavirus, the rash was their only symptom.

The rashes associated with COVID-19 fall into three categories:

• Hive-type rash (urticaria): Sudden appearance of raised bumps on the skin which come and go quite quickly over hours and are usually very itchy. It can involve any part of the body, and often starts with intense itching of the palms or soles, and can cause swelling of the lips and eyelids. These rashes can present quite early on in the infection, but can also last a long time afterwards.
• ‘Prickly heat’ or chickenpox-type rash (erythemato-papular or erythemato-vesicular rash): Areas of small, itchy red bumps that can occur anywhere on the body, but particularly the elbows and knees as well as the back of the hands and feet. The rash can persist for days or weeks.
• COVID fingers and toes (chilblains): Reddish and purplish bumps on the fingers or toes, which may be sore but not usually itchy. This type of rash is most specific to COVID-19, is more common in younger people with the disease, and tends to present later on.

Although COVID-19 is often thought of as a virus that affects the respiratory system, rashes had been reported in a number of cases of people in China and Europe who had been hospitalised with severe symptoms of the disease. However, this is the first and largest study to systematically gather data about skin rashes in milder cases in the wider population.

Lead author Dr Veronique Bataille, consultant dermatologist at St Thomas’ Hospital and King’s College London said: “Many viral infections can affect the skin, so it’s not surprising that we are seeing these rashes in COVID-19. However, it is important that people know that in some cases, a rash may be the first or only symptom of the disease. So if you notice a new rash, you should take it seriously by self-isolating and getting tested as soon as possible.”

Consultant dermatologist Dr Justine Kluk said: “These findings highlight the importance of keeping an eye on any new changes in your skin, such as lumps, bumps or rashes. Early reporting of COVID-associated rashes by members of the public and recognition of their significance by frontline healthcare practitioners - such as GPs, NHS 111 and hospital staff - may increase the detection of coronavirus infections and help to stop the spread.”

Want more of the latest science news straight to your inbox? Become a SelectScience member for free today>>