Erythema multiforme and urticaria may be associated with a better outcome with coronavirus disease 2019 (COVID-19), a letter from academic dermatologists to the editor of Dermatologic Therapy suggests, but more data are needed to confirm this theory.

In their letter, research dermatologists from the Magna Graecia University of Catanzaro in Italy mention that both erythema multiforme and urticaria can sometimes be associated with eosinophilia, which is defined as having an eosinophil count of >500 eosinophils/mm3. Recent case reports have documented erythema multiforme and urticaria in patients with COVID-19, with drug eruption representing a common triggering factor. Currently, eosinophilic cell blood counts are involved in the diagnosis and prognosis of COVID-19, as eosinopenia has recently been associated with up to 81% of infection cases.

As such, eosinopenia may be a good marker for COVID-19 diagnosis, the investigators noted. In addition, persistent eosinopenia has been associated with higher mortality in patients with the virus. Another case report, however, suggests that increased blood eosinophils correlate with an improvement in the overall condition of a patient with the infection. Also, other patient data indicate that patients with a pre-existing atopic disease may be less affected by the novel coronavirus. Based on these reports, it has been suggested that eosinophilia may act as a protective factor against the development of COVID-19.

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The researchers of this letter suggest that eosinopenia may be secondary to either stress-induced glucocorticoid secretion or cell depletion due to the viral infection. In addition, eosinophilia exerts an antiviral effect, as shown previously in reports of the influenza virus.

Also, the occurrence of non-drug-induced erythema multiforme appears to be mostly sequestered in young and otherwise healthy nonhospitalized patients with COVID-19. The authors suggest that the non-drug-associated erythema multiforme and urticaria conditions may correlate with systemic “eosinophilia secondary to a strong response to COVID-19, and therefore possibly to a better outcome of the disease.”


Dastoli S, Bennardo L, Patruno C, Nisticò SP. Are erythema multiforme and urticaria related to a better outcome of COVID-19? [published online May 24, 2020]. Dermatol Ther. doi: 10.1111/dth.13681