The most common symptoms of COVID-19 are fever, dry cough, and loss of the sense of taste and smell. Other frequently seen signs include headaches, muscle and joint pain, nasal congestion, and fatigue.
A less common symptom is skin rashes of various forms. These have been slower to report, in part due to the wide variety that has appeared in COVID-19 patients, making it more difficult to establish a consistent correlation.
However, it is important to know how COVID-19 affects the skin. A recent study found that for 17 percent of COVID-19 patients with multiple symptoms, skin rashes were the first symptom to appear, while for 21 percent of patients, rashes were their only symptom.
Being able to identify the effects of COVID-19 on the skin can allow cases to be detected earlier, or even fully detected in people who are otherwise asymptomatic. This could help limit transmission.
With that in mind, here are the four main types of skin changes to watch out for and the possible reasons why they occur.
These are reddened, inflamed or blistered skin lesions that mainly affect the toes and soles of the feet, known colloquially as “COVID toes.” Over the course of one to two weeks, the lesions will further discolor and flatten, after which they will spontaneously resolve without treatment.
A substantial number of these injuries have been seen, primarily in adolescents and young adults with no or only mild symptoms of COVID-19. They make up the majority of skin problems associated with the virus. In two international reports on different types of skin conditions presumably related to COVID, about 60 percent of patients with skin complaints reported these lesions.
However, since these lesions correlate with mild illness, many of the patients with them in these studies did not qualify for a COVID-19 test at the time, and 55 percent were otherwise asymptomatic.
So while the rapid increase in these injuries during the pandemic suggests they are associated with COVID-19, no direct confirmation of this has been established. It is possible that they are caused by some other related factor.
It’s also unclear when exactly they appear. In a study that looked at 26 patients with suspected COVID-related skin changes, 73 percent had chilblain-like lesions. None of the patients had respiratory symptoms and all were COVID negative at the onset of the lesions. One explanation is that these lesions appear only after a long period of time, up to 30 days after infection.
The cause of these injuries has been debated. A possible culprit could be type 1 interferons, proteins that regulate the antiviral properties of the immune system.
The theory is that high production of these interferons could result in patients quickly shedding the coronavirus, but also cause blood vessel injury and increased inflammation. This would explain the coincidence of mild or non-existent disease, negative tests, and skin damage.
Another theory concerns ACE2, the molecule that the coronavirus uses to enter cells. It is present in many types of cells, including those of the sweat glands, which are common on the palms of the hands and the soles of the feet. This could make these areas particularly vulnerable to damage from the virus.
Or it could be that the damage to the blood vessels, caused by the immune response or the virus, causes cell death and multiple mini blood clots in the toes.
This term describes flat, raised areas of discolored skin. A study of 375 patients in Spain found that 47 percent of patients with COVID-related skin changes had this type of rash.
These were associated with more severe COVID-19 symptoms and were found primarily on the trunk in middle-aged to elderly patients. They usually last between 7 and 18 days, appearing between 20 and 36 days after infection.
One suggested cause is that the body’s immune system is speeding up. In some patients, a hyperinflammatory phase occurs 7 to 10 days after infection, leading to tissue damage and potentially more serious illness and death.
Also known as hives, they are raised areas of itchiness on the skin. In a study involving four hospitals in China and Italy, 26 percent of COVID-19 patients who complained of skin changes developed hives.
Hives often precede or present at the same time as other symptoms, making them useful for diagnosis. They are more common in middle-aged patients and are associated with more serious illness. Viral infections are a known trigger for hives, as they cause the degradation of cells and the release of histamine through a cascade of reactions in the immune system.
However, it is important to remember that hives are also a known side effect of many medications that have been used to treat COVID-19, such as corticosteroids and remdesevir.
These are clear fluid-filled sacs under the skin, similar to those seen in chickenpox. They are less common compared to previous skin conditions: In the aforementioned Spanish study of skin changes associated with COVID-19, only 9 percent of patients had these vesicles.
However, they are believed to be a more specific indication that someone has COVID-19 than those already on the list, so they are more useful for diagnosis. They appear to occur in patients with mild illness about 14 days after infection.
They are believed to be caused by prolonged inflammation, with antibodies attacking the skin and damaging its layers, resulting in fluid-filled sacs.
Vassilios Vassiliou, Senior Clinical Professor of Cardiovascular Medicine, University of East Anglia and Subothini Sara Selvendran, Visiting Research Fellow in Medicine, University of East Anglia.
This article has been republished from The Conversation under a Creative Commons license. Read the original article.