During winter, it is common for there to be an increase in cases of flu, Covid-19 and other respiratory infections, due to the characteristics of the season and staying indoors, in addition to the greater circulation of viruses. Although many people recover from these illnesses within a few weeks, some may notice, around two to three months later, intense hair loss, called telogen effluvium.

“Infections are well-established causes of telogen effluvium. What happens during and after infections is that there is an intensely inflammatory state capable of ‘deprogramming’ the normal cycle of the follicles and interrupting the growth phase of many hairs, taking them to the shedding (telogen) phase. It is as if the body signals to the hairs that their growth is not the priority at that time of great metabolic stress. This process is generally diffuse, self-limited and reversible”, explains Dr. Natalia Cymrot, dermatologist member of the Brazilian Society of Dermatology – São Paulo Regional (SBD-RESP).

When the body faces an infection, it intensifies the action of the immune system, releasing cytokines and other inflammatory mediators that help eliminate viruses or other disease-causing agents. “This process, associated with the increase in hormones related to physiological stresssuch as cortisol, and the temporary reduction in the supply of oxygen and nutrients to hair follicles, can prematurely interrupt the hair growth phase”, says Dr. Daniel Cassiano, dermatologist and director of SBD-RESP.

According to the doctor, this process causes a greater number of hairs to enter the hair loss phase prematurely, giving rise to telogen effluvium. “In general, the more intense or prolonged the infection, the greater the impact on the hair cycle tends to be”, he highlights.

Infections that can trigger telogen effluvium

According to Dr. Natalia Cymrot, a simple flu can cause telogen effluvium, but more severe and prolonged infections are more likely to trigger it, especially if there is a high fever. “In the case of Covid-19, the disease causes intense inflammation, which lasts for months after the period of positive tests. Furthermore, there may still be coagulation changes with the formation of microthrombi and a possible direct effect of the virus on the hair follicle, which greatly increases the chance of telogen effluvium. In practice, it is extremely common to observe effluvium in post-Covid-19 patients”, he says.

In addition to Covid-19, other infections that cause an intense inflammatory response in the body can also affect the hair growth cycle. “But many other infections, especially the more serious, prolonged ones that involve high fever and hospitalization, are also associated with the appearance of telogen effluvium, such as pneumonia, scarlet fever, whooping cough, tuberculosis, malaria, dengue fever, HIV, Influenza”, adds the doctor.

The severity of the infection is related to the increased chance of having the condition. “Moderate/severe conditions, requiring hospitalization, which include anemia, hormonal dysfunctions, diabetes, nutritional deficiencies, are more likely to trigger effluvium”, comments Dr. Natalia Cymrot.

How long does hair loss last?

Generally, telogen effluvium appears between 1 and 3 months after infection, although there may be earlier cases, which begin 2 to 3 weeks after infection, which is rarer. “The duration also varies from 1 to 3 months and the hair recovers between 6 and 12 months later. It is a process that is generally self-resolving”, says Dr. Daniel Cassiano.

Overall, to prevent the condition, proper control of infection and inflammation can prevent serious complications and reduce the risk of damage to hair follicles. “The post-covid period, for example, is associated with deficiencies in iron, vitamin D, B12 and ferritin (even with normal iron) in many patients, which must be corrected, as it favors the appearance of effluvium. As far as possible, reducing stress, adequate sleep and psychological support are a central part of prevention management”, comments Dr. Natalia Cymrot.

How to differentiate telogen effluvium from other types of hair loss

According to the Brazilian Society of Dermatology – São Paulo Region, telogen effluvium presents remains diffuse of hair, without well-defined flaws, and the traction test shows many strands coming out. “The hairs fall out in large quantities when bathing, pillows, brushing; but on examination it is possible to see many short hairs growing over the months”, explains Dr. Natalia Cymrot.

However, the evolution of the decline over time must be observed. “Although telogen effluvium in the vast majority of cases is benign and self-limited, it is important to investigate when the hair loss has a different pattern or persists beyond 6 months, which may suggest chronic telogen effluvium or another type of alopecia”, highlights the dermatologist.

The medical entity informs that alopecia such as androgenetic or areata have different patterns of distribution, evolution and trichoscopic findings, and usually justify early evaluation by a dermatologist. “We should raise suspicion of other alopecias when there are well-defined areas of rarefaction (entrances/frontal typical of androgenetic alopecia) or plaques (suggests alopecia areata, cicatricial, etc.), instead of diffuse hair loss”, says Dr. Daniel Cassiano.

According to Dr. Natalia Cymrot, the alert also extends when there are inflammatory signs on the scalp, such as significant pain, redness and intense flaking. “If there is history of other autoimmune diseasesendocrine symptoms, marked weight loss, bleeding, use of certain medications, or any worrying systemic sign, additional investigation with trichoscopy, biopsy and laboratory tests is mandatory”, he states.

Monitoring is essential during hair recovery

Dr. Natalia Cymrot highlights that this form of hair loss is usually temporary and, in most cases, the hair recovers spontaneously. “Supplementation of possible nutritional deficiencies is important, if any. Some articles mention the use of topical or oral minoxidil, although there is still little specific evidence for post-infection telogen effluvium. Stimulating the scalp with some types of lasers and microneedling can help recover hair growth”, concludes the doctor.

By Maria Claudia Amoroso