COVID Rash · What Is It, Signs, Symptoms, Treatment, and More

COVID rash is a general term to describe the skin manifestations associated with COVID-19 infection. COVID-19, or coronavirus disease discovered in 2019, is a respiratory infection caused by severe acute respiratory syndrome coronavirus 2, or SARS CoV-2, virus. Although COVID-19 is best known for causing respiratory symptoms, it has also been associated with several extrapulmonary manifestations, including cardiac dysfunction, renal failure, gastrointestinal symptoms, and skin manifestations. 

Skin manifestations of COVID-19 are grouped into five major categories, including morbilliform rashes, which contain rose-red flat or slightly elevated lesions, resembling measles; urticaria that involves itchy, red welts; vesicles which are small blisters; pseudo-chilblains, also known as “COVID toes,” involving painful inflammation of the toes in response to cold; and vaso-occlusive skin lesions due to thrombosis and occlusion of small arteries. 

The exact cause of skin involvement in COVID-19 is not clear. However, research suggests it may be associated with how SARS-COV-2 enters the cells. SARS-COV-2 is a virus that enters the body through the angiotensin-converting enzyme 2 (ACE2) receptor, which is found in epithelial cells of various body tissues, including the skin. The primary role of the ACE2 receptor is to modulate the function of angiotensin II, a protein essential for regulating blood pressure. ACE2 converts angiotensin II to other molecules that counteract angiotensin’s harmful effects, such as increased cell inflammation. When SARS-COV-2 binds to ACE2 receptors on the surface of cells, the receptor’s action is inhibited, thereby making more angiotensin II available to tissues.  It’s thought that the accumulation of angiotensin II contributes to lung damage, blood vessel dysfunction, and increased vascular permeability, which may lead to skin rashes. 

Another possible theory is that COVID-19 particles in cutaneous blood vessels may disturb the immune system response and trigger the release of pro-inflammatory molecules, resulting in blood vessel inflammation, microvascular injury, thrombotic events, and occlusion of small arteries.  

The most common skin manifestations of COVID-19 are morbilliform rashes, which consist of an itchy, generalized, maculopapular rash with flat or slightly elevated lesions that are rose-red.  

Urticaria, also known as hives, is also common in COVID-19. Clinical features typically consist of raised, well-defined wheals that are usually red, blanch with pressure, are incredibly itchy, and can present anywhere on the body, most commonly the trunk. 

Next, vesicular eruptions may also occur in the setting of COVID-19, either localized or distributed throughout the body. Both urticaria and vesicles appear before the onset of the other general COVID-19 symptoms.  

Pseudo-chilblains, on the other hand, were the first noted cutaneous manifestations associated with COVID-19. However, their link with COVID infections has since been debated. Pseudo-chilblains consist of small, itchy swellings on the skin that occur as a reaction to cold temperatures and most commonly affect the body's extremities, such as the toes, fingers, heels, ears, and nose. The lesions are usually asymmetrical and are seen in younger individuals.  

Finally, vaso-occlusive lesions have been reported in individuals with COVID-19 with several different presentations, including livedo reticularis, purpuric lesions, and acral ischemia. These lesions are most frequently seen in hospitalized individuals with moderate to severe COVID-19 and are associated with more severe disease than the other skin manifestations.  

Differential diagnoses involve considering various possible conditions that could be causing symptoms and then ruling out each one through use of history, clinical evaluation, diagnostic tests, and critical thinking. This process helps to narrow down the list of potential diagnoses to determine the most likely cause of the symptoms. 

Differential diagnoses can be broken down into four categories: most likely, less likely, least likely, and can’t miss. Most likely diagnoses are conditions most probable based on symptoms and clinical presentation. Less likely diagnoses are not as probable but should still be considered. On the other hand, least likely diagnoses can be considered if other, more probable conditions are excluded. Finally, can’t miss diagnoses are less common but critical to promptly identify and treat as they can lead to severe consequences.