Like most mammals, humans “shed” every day as part of the natural cycle of hair growth. After an illness or period of stress, however, it’s not uncommon to lose many more hairs than usual. Hair loss also often occurs during pregnancy, in those with poor nutrition, or after a major psychological trauma. Any serious illness, especially one that involves fever, can lead to excess hair shedding, and Covid-19 is no exception. Fortunately, this typically resolves on its own within about a year.
In healthy people, hair growth follows three stages that take place within the individual hair follicles: the active growth stage (anagen) lasts between two and six years, followed by a brief transitional stage (catagen) in which the hair shrinks and detaches from the follicle as it prepares to fall out, then finally a resting phase (telogen) that lasts about three months before the anagen phase starts again. About five to ten percent of your hair is in the telogen phase at any given time, with hairs falling out during everyday combing, brushing, and washing, or as they get pushed out by the new hair growing up from below. After an illness or a period of emotional or physical stress, however, half or more of your hairs may go into the telogen phase at the same time, a condition called telogen effluvium, marked by a noticeable increase in the number of hairs falling out each day.
Hair shedding usually begins two or three months after the triggering illness or trauma and may last six to eight months after recovery. As the anagen phase begins again, hair growth resumes its normal cycle.
One study of more than 500 people who had Covid-19 in the first few months of the pandemic found 10 who experienced telogen effluvium. In that group, researchers were unable to determine if the hair loss was entirely due to the illness or to the medications used to treat it. A later study, published in August 2021, controlled for medication; researchers evaluated 39 Covid-19 patients who were experiencing hair loss during their recovery and concluded that the excess shedding could be attributed to the viral infection. JAAD International, a companion to the Journal of the American Academy of Dermatology, reported on a survey of 128 patients worldwide who sought medical help for hair loss after infection with Covid-19 and found that nearly two-thirds of the patients had telogen effluvium. In this report, patients with more severe cases of Covid appeared to experience more significant hair shedding.
Hair loss can be distressing, but telogen effluvium is generally self-limited. Good nutrition is closely related to hair health, so be especially attentive to your diet during recovery and your hair should be back to normal within a year.
Andrew Weil, M.D.
Sharquie KE, Jabbar RI. “COVID-19 infection is a major cause of acute telogen effluvium.” Ir J Med Sci. 2021 Aug 31:1–5. doi: 10.1007/s11845-021-02754-5. Epub ahead of print. PMID: 34467470; PMCID: PMC8407603. https://pubmed.ncbi.nlm.nih.gov/34467470/
Olds H, Liu J, Luk K, Lim HW, Ozog D, Rambhatla PV. “Telogen effluvium associated with COVID-19 infection.” Dermatol Ther. 2021 Mar;34(2):e14761. doi: 10.1111/dth.14761. Epub 2021 Jan 14. PMID: 33405302; PMCID: PMC7883200. https://pubmed.ncbi.nlm.nih.gov/33405302/
Starace, Michela et al. “Trichodynia and telogen effluvium in COVID-19 patients: Results of an international expert opinion survey on diagnosis and management.” JAAD international vol. 5 (2021): 11-18. doi:10.1016/j.jdin.2021