Medication-Induced Hair Loss: An Update

The document discusses the link between COVID-19 vaccines and the development of alopecia areata (AA), including its extensive variants alopecia totalis and alopecia universalis. The incidence of AA has significantly increased after COVID-19 vaccination, with 116 cases reported in the United States after Pfizer/BioNTech and Moderna vaccines, and 154 cases in the United Kingdom, mainly after Pfizer/BioNTech and AstraZeneca vaccines. The onset time of AA varies from a few days to several weeks after vaccination. The possible mechanism is that COVID-19 vaccines induce spike protein, leading to molecular mimicry phenomena, which can produce pathologic autoantibodies that may attack the hair bulb and cause AA. The vaccines may also exacerbate the production of interleukin 6, interferon gamma, and tumor necrosis factor-alfa, which are involved in AA pathogenesis. Other vaccines, such as hepatitis B, poliovirus, zoster, influenza, and human papillomavirus vaccines, have also been associated with AA.