Why Stress Sparks Hair Loss, According to Mice

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IIf you’ve ever seen your hair pile up in the shower drain during a particularly stressful time in your life, you’re not alone: ​​hair loss due to stress is very common. Yet scientists are still trying to determine precisely how stress impacts our bodies, particularly on rapidly regenerating tissues like hair follicles, which are more vulnerable to sudden changes in the body.

Stress is linked to two hair loss disorders: telogen effluvium, a usually temporary condition that can cause significant hair loss, and alopecia areata, an autoimmune disease that is often chronic. To learn more about how such conditions arise, scientists induced stress in mice, which are frequently studied to better understand hair growth and loss, and observed how their hair follicles reacted.

This quickly activated the sympathetic nervous system, which coordinates the “fight or flight” response to perceived threats. These nerves then release a large amount of the neurotransmitter norepinephrine, which in excess can kill rapidly multiplying cells in the hair follicle, a finding reported in the journal Cell.

Read more: »Why do marine mammals lose their hair»

This damage was temporary, the authors noted, because it did not affect the stem cells that help sprout new hair. But upon closer inspection, scientists observed that stress was behind another phenomenon: in mice, the body seemed to view inflamed or dead hair follicles as unwanted visitors. This triggered a flood of immune reactions. T cells, which protect the body from disease, “now view hair follicles as a foreign object that they should attack,” study author Ya-chieh Hsu, a stem cell scientist at Harvard University, said in a statement.

This attack could cause longer-term damage: The much-publicized T cells could continue to hit hair follicles when the animals face stress in the future, the scientists noted. If similar processes are underway in the human body, this could explain how alopecia areata appears and why most people with the condition relapse throughout their lives.

The trigger for autoimmunity “remains one of the biggest mysteries,” the authors write in the paper, but this paper could help scientists better understand how environmental factors, including stress, contribute to it. “You always need a trigger, and the trigger is not necessarily genetic,” Hsu said in the release.

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Main image: Jahin934 / Shutterstock

• Molly Glick

  Published on December 4, 2025

  Molly Glick is the newsletter editor of Nautilus.