Little is known about the possibility of hair loss in patients recovering from coronavirus disease 2019 (COVID-19). Although a minor loss, it seems devastating to many people and has been studied by several researchers.
A new article published in the Journal of Cosmetic Dermatology summarizes what is known about this potentially distressing condition.
COVID-19 is marked by its plethora of manifestations, which vary greatly from one individual to another. Hair loss is quite common after acute infections or autoimmune diseases. Previous illnesses caused by coronaviruses, such as the outbreaks of severe acute respiratory syndrome and Middle East respiratory syndrome (SARS and MERS, respectively), have also been associated with alopecia.
In COVID-19, it is thought to affect around one in five people, spanning a wide range of categories – telogen effluvium (TE), worsening male pattern baldness, and alopecia areata (AA), to name a few.
The authors of this article explored the reversibility, duration, association with severity, and possible causes of hair loss associated with COVID-19. They reviewed all eligible articles published on the topic, including randomized controlled trials (RCTs), case-control studies, and prospective or retrospective cohort studies.
The search turned up 26 articles, of which 17 were case reports and the rest observational studies. Of these, most had no comparison group. Five of the six observational studies looked at ET, when large numbers of hair follicles enter the resting phase in response to stress or other disorders.
These researchers often found that ET began 45 to 50 days after the onset of infection and resolved spontaneously in the majority of cases. Eight of these studies suggested that TE was correlated with COVID-19.
A large Korean study retrospectively examined AA in COVID-19, finding no correlation between the two. Most of them were small studies.
Regarding case reports, most hair loss patients were female and ET was the predominant form, reported in three quarters of cases. AA was found in 5%. Most patients have lost their hair within three months of diagnosis.
Of the 20 patients whose results were described, nearly all reported recovering from hair loss after a median of five months. Nearly 40 patients described their treatment, most with topical lotions containing clobetasol or minoxidil, and one with low-dose systemic corticosteroids.
Two patients had oral hydroxychloroquine or minoxidil. About one in five were not treated medically except to reassure themselves.
This first scoping review shows that hair loss occurs in a proportion of COVID-19 cases and is mostly reversible. Most patients take a few weeks to a few months to recover hair growth. No clear association was made with the severity of COVID-19, but female patients appeared to be at higher risk for alopecia with this condition.
Since hair loss was mostly self-reported and clinically confirmed, these studies need to be followed by more detailed and validated research.
The incidence of hair loss in long Covid patients remains unknown, as long-term follow-up was lacking. Theories of the cause include severe inflammation in some COVID-19 patients, with elevated levels of cytokines like interleukin-(IL)6, which suppress hair shaft elongation and hair follicle proliferation. However, most patients with hair loss appear to have had only mild disease.
Estrogen and progesterone, female hormones, may play a role in hair loss during COVID-19, as most of these patients were female. These have anti-inflammatory effects, estradiol acting on the hair follicles to promote their growth and improve the hair cycle. Progesterone can reduce the conversion of testosterone to its active form, which is linked to alopecia.
Both of these hormones have immunomodulatory effects. They are being studied for their potential use in the treatment of COVID-19.
Acute COVID-19 can alter the balance of these hormones or lead to a reduction in their levels, resulting in female-dominated hair loss. Further studies will be needed to validate this hypothesis and to understand other pathophysiological mechanisms.
A small number of patients had long-term alopecia without any clear underlying disease process being identifiable. Clinical awareness of this symptom is likely to increase, especially since only the most severe cases may have presented to the clinician.