Hair loss has become a widely reported symptom experienced by many individuals recovering from a COVID-19 infection. This distressing side effect is not a direct result of the virus attacking the hair itself but rather a delayed reaction to the immense physiological shock the body endures during the illness. Studies indicate that a significant percentage of patients notice an increase in hair shedding months after their initial recovery. This article explores the biological mechanism behind this phenomenon and provides a clear understanding of the expected timeline for recovery.
Understanding the Hair Growth Cycle and Telogen Effluvium
Hair growth on the scalp is a continuous, cyclical process that involves three primary stages. The first and longest stage is the anagen phase, the period of active growth that can last anywhere from two to seven years. Approximately 85 to 90 percent of the hairs on a healthy scalp are in this growing phase at any given time.
Following the anagen phase is the catagen phase, a short transitional period lasting only a few weeks where the hair follicle shrinks and growth stops. The final stage is the telogen phase, a resting period that lasts about three months before the hair is naturally shed and the cycle restarts. Normally, only about 10 to 15 percent of hairs are in this resting phase, resulting in the typical daily shedding of 50 to 100 hairs.
The significant hair loss associated with COVID-19 is medically defined as Telogen Effluvium (TE). This condition occurs when a major systemic shock prematurely interrupts the active growth (anagen) phase, forcing a much larger than normal percentage of hairs into the resting (telogen) phase simultaneously. TE is a reactive process, meaning it is an observable response to a disturbance impacting the body’s overall system. The noticeable shedding begins only after the three-month resting period is complete, creating a clear delay between the illness and the hair loss.
How the COVID-19 Infection Triggers Hair Shedding
The COVID-19 infection acts as a trigger for Telogen Effluvium through a combination of physiological stressors. One primary factor is the presence of a high fever, which signals the body to redirect resources toward survival and away from non-essential processes like hair production. This systemic shock causes a sudden cessation of the hair growth cycle across the scalp.
A second mechanism involves the body’s intense immune response to the SARS-CoV-2 virus. When the immune system fights the infection, it releases pro-inflammatory signaling molecules called cytokines. This inflammatory surge can disrupt the signaling pathways necessary for healthy hair follicle function. These high levels of inflammatory markers prematurely push growing hair follicles into the transitional and resting phases.
Furthermore, the viral infection can affect the body’s vascular system, leading to the activation of the coagulation cascade. This can result in the formation of tiny blood clots, known as microthrombi, which may occlude the fine blood vessels supplying nutrients to the hair follicles. Reduced blood supply to the follicle stresses the hair matrix cells, contributing to the premature shift into the shedding phase.
The emotional and psychological stress associated with a severe illness also plays a contributing role. Prolonged anxiety and physical exhaustion can independently trigger Telogen Effluvium, compounding the effects of the fever and inflammation induced by the virus. These combined biological and psychological shocks overload the hair cycle’s regulatory systems, culminating in the delayed, diffuse hair shedding.
Duration and Management of Post-COVID Hair Loss
The hair shedding typically begins two to three months after the initial onset of the COVID-19 infection, aligning with the three-month resting period of the telogen phase. This delay often leads people to mistakenly believe the hair loss is unrelated to their past illness. For the majority of people, this condition is self-limiting and temporary, with the excessive shedding phase lasting approximately three to six months.
Once the initial trigger is removed, the hair follicles remain intact, and normal hair growth begins to resume. Full recovery, where hair density returns to pre-shedding levels, is expected within six to nine months from the start of the shedding. Noticeable improvements in thickness and volume require patience, as hair grows slowly.
Supportive measures can help promote a healthy environment for regrowth. Maintaining a balanced, protein-rich diet and ensuring adequate levels of micronutrients like iron (ferritin) and Vitamin D is beneficial, as deficiencies can prolong the shedding. Gentle hair care, such as avoiding tight hairstyles and minimizing heat styling, can also prevent further breakage.
If the hair shedding persists for longer than nine months, or if the loss is localized and patchy rather than diffuse, consulting a dermatologist is recommended. A specialist can rule out other underlying conditions, such as thyroid dysfunction or autoimmune issues. The most important step in managing this post-viral effect is understanding that the hair loss is a temporary reaction to stress, and the hair follicles retain their capacity for regrowth.