In the months following a Covid-19 infection, many people have reported increased hair loss—a phenomenon experts say is relatively common, and likely temporary, Knvul Sheikh writes for the New York Times.

How common is hair loss after Covid-19?

Research estimates that 22% of patients hospitalized with Covid-19 experience sudden and temporary hair loss—known as telogen effluvium—following an infection. 

While it is more difficult to determine how common hair loss is in people who experienced mild forms of Covid-19, studies suggest that it is one of over 60 persistent symptoms typically associated with long Covid.

Throughout the Covid-19 pandemic, many doctors have observed an increase in patients seeking help for the condition. "I have never seen anything like it in my life," said Michele Green, a New York City-based dermatologist who is affiliated with Northwell Health's Lenox Hill Hospital and specializes in hair loss. "I'm seeing more male and female patients, from every age group, every working profession. It's really been across the board."

What causes increased hair loss after Covid-19?

According to Sheikh, telogen effluvium "occurs when stress or illness triggers much more shedding than the typical 50 to 100 hairs a person loses per day."

Notably, the condition is not specific to Covid-19. "Experts have known for centuries that severe illness, surgery, blood loss, hospitalization, childbirth and extreme emotional events, like the loss of a loved, one can trigger telogen effluvium," Sheikh writes.

However, evidence suggests that people who have a history of Covid-19 infection are four times as likely to experience hair loss than those who have no history of infection.

While experts do not fully understand how physical and emotional stressors cause telogen effluvium, many dermatologists believe a stress hormone called cortisol may play a part.

However, Luis Garza, a professor of dermatology at the Johns Hopkins University School of Medicine, noted that other chemicals may provide a signal telling hair follicles when to shed.

For many, "Covid-19 has been a double whammy," combining "the mental stress of living through a pandemic" with "the physical stress of the illness itself," Sheikh writes.

Typically, individual hairs cycle through three phases—the anagen phase, catagen phase, and telogen phase—before falling out. The follicle then repeats the entire process. Each strand goes through different phases of the cycle at different times, meaning that only 5% to 10% of a person's hair on their head should be in the telogen phase at any point in time.

"Telogen effluvium short-circuits the cycle for many hairs," Garza said. When this happens, 30% to 50% of a person's hair enters the telogen phase, which leads to large amounts of hair falling out two to three months after an illness.

Fortunately, the hair loss is usually temporary. Experts have noted that while it may last between six and nine months, the shedding eventually slows, and new hair starts to grow.

What should you do if you are experiencing hair loss after Covid-19?

According to Sheikh, you should see a doctor if you notice sudden hair loss or are concerned about the amount of hair you are losing. "By intervening early, particularly if your hair loss is linked to an underlying condition, you can treat it effectively," Sheikh writes.

"Usually you'll know if you're losing hair long before anyone can actually clinically see it," Green said.

Typically, doctors record your medical history, order blood work, and perform a hair-pull test, which involves gently pulling small sections of hair from different areas of a patient's scalp. "If six or more strands fall out without resistance, it is a positive indicator of active loss," Sheikh writes. "In some cases, your doctor may also order a biopsy to examine your hair follicles."

If a patient has telogen effluvium, most doctors will suggest waiting for the hair to grow back on its own.

"A lot of what I do is counsel people when it occurs and play the role of a cheerleader for them, reassuring them that this will get better," said Arash Mostaghimi, director of dermatology inpatient service at Brigham and Women's Hospital.

However, some dermatologists may recommend a topical solution of minoxidil—the hair-growth drug that is the active ingredient in Rogaine.

According to Garza, stress management can often be an effective way to address the condition. "One thing I tell patients who come in for hair loss is that they might benefit from seeing a therapist, because we know that stress causes hair loss and hair loss also adds to stress," he said. "Hair is a huge component of our identity."

While some people turn to supplements that are not well-regulated to boost their hair growth, Mostaghimi noted that most people's diets already include enough of the vitamins and minerals needed for good hair growth. "I discourage people from being too aggressive in trying these because you may end up spending a lot of money on these items when the benefits are marginal if any," Mostaghimi said.

Ultimately, experts emphasize that telogen effluvium following Covid-19 is not usually permanent.

"The majority of my patients who came to me in the beginning of the pandemic are already doing better," Mostaghimi said. "Their hair has recovered and they are able to express themselves with their hair the way that they want." (Sheikh, New York Times, 9/30)