The skin has solar memory. We know that every sunburn leaves a mark in the form of permanent damage that translates into spots, photoaging and a higher risk of cancer.
The scalp is also skin and, in its own way, also suffers from excessive sun exposure. Recent studies conducted by Sisley laboratories reveal that scalp microbiota imbalances deteriorate hair health and could accelerate its shedding.
In this process, a sunburn on the scalp, what trichologists call ‘solar erythema’, could have worrying consequences for the mane.
At the beach, better with a hat
José Ginestar, scientific director of Sisley, explains that “that scalp erythema produces inflammation. Our studies have detected the presence of two specific bacterial strains that recur in the scalp microbiota of people with alopecia. These strains would be responsible for a chronic inflammation that could favor hair loss.”
The conclusions of the study carried out by Sisley show that this inflammation speeds up the hair life cycle, which under normal conditions lasts between 2 and 8 years. When this inflammation occurs, hair falls out sooner and the reserves could be depleted. “Among the causes we have identified are the leakage of stem cells, the loss of anchorage, and the decline of cellular energy.”
This action would not be instantaneous, but, like everything related to the skin, happens in the future, though inexorably.
In the future, will we all be bald?
It is estimated that a scalp follicle can complete approximately between 10 and 30 cycles over a lifetime. The question floating around is whether accelerating that cycle due to inflammation could exhaust the follicle’s lifetime reserves.
This extreme has not yet been scientifically demonstrated and Ginestar avoids the worst-case scenario. “What matters to us is having healthy hair and for that the anagen phase lasts as long as possible. We know that solar erythema and inflammation shorten the anagen phase, so that is what we must avoid. Obviously, the problem is greater the fewer hairs we have because it’s easier to damage the scalp with the sun,” he adds.
In a longevity-focused context as a vital objective, losing hair prematurely could become a problem if we want to reach a hundred years with a good mane. “I insist: prevention is best. If we go to the pool, it’s no trouble to wear a hat or a scarf. And at home, after washing it, apply Le Sérum Revitalisant Fortifiant de Hair Rituel by Sisley. A tip I always give is to do an intensive course at the equinoxes, when hair loss is greatest. We’ll start applying it every two days and then twice a week.”
Laboratory results show that this achieves 50% fewer hairs in the shedding phase and an intense and significant reactivation of hair growth.
The Hair Life Cycle
Each hair follicle repeatedly goes through a cycle that includes a growth phase or anagen, a brief transition phase or catagen, and a resting phase or telogen, after which the hair finally sheds. Under normal conditions, the follicle then starts a new cycle and produces a new hair that will again pass through these phases. “The 10-30 cycles figure is indicative. There is no evidence that occasionally speeding up the hair cycle means ‘spending’ a limited reserve of cycles and ending up bald from having consumed them too soon,” notes trichologist Cristina Romera, from the Ricart Medical Institute.
She explains that the hair follicle has a strong regenerative capacity thanks, among other mechanisms, “to the presence of follicular stem cells, which participate in the start of each new cycle.”
“With age, the follicle also ages and may lose part of its regenerative capacity. In this process, complex mechanisms related to follicular stem cells, oxidative stress and other aging-associated changes play a role. We cannot say this happens simply because we have consumed a certain number of cycles. The right approach is to talk about factors that can alter the normal functioning of the follicle,” the trichologist adds.
Warmer summers, baldness guaranteed?
Dr. Javier Fernández Vela, a trichologist at Esthea Medica, says we must distinguish between heat and solar radiation. “Ultraviolet radiation can produce numerous biological effects on the skin, but this does not prove that higher ambient temperatures shorten the anagen phase to exhaust the follicles. There is no basis to think that increasingly warm summers will cause long-lived people to end up bald by accelerating and prematurely exhausting their hair cycles. In other words: the scenario of reaching 100 or 120 years old as ‘billiard balls’ because heat has caused us to spend all our hair cycles is not supported by these dermatological sources.”
He calls for calm in the face of the dreaded seasonal shedding that occurs every autumn. “We know that hair loss shows seasonal variations. That is, over the year the proportion of hairs in the different phases of their cycle can change. But the existence of a seasonal variation does not mean the cause is heat, let alone that every summer we are consuming part of a limited hair reserve. In a healthy person, we do not need to try to indefinitely delay telogen. For hair to stop growing, go into rest, shed and be replaced by another is part of the normal physiology of the follicle,” he adds.
The Sun Is Not Bad, Unless You Burn
The theory that solar erythema is another factor in damaging follicle health is solid. It is not as clear the relationship between summer heat or the fact that there are more daylight hours in that season. Dr. David Saceda, a collaborating trichologist with Unicskin, clarifies that “in summer and after summer there is a reactive hair shedding. It is a temporary shedding, but science does not clearly know why it happens.”
One hypothesis is heat. “It could also be due to solar radiation, not so much the burns, but that sunlight increases through spring to reach its maximum in summer. More hours of light per day shift our circadian rhythm and the body interprets it as a moment to renew the coat of hair, as happens in other mammals,” adds Dr. Saceda.
What We Can Do
Hair health, like skin health, largely depends on how we care for it. “Yes, we can lengthen the life cycle of each hair. First, before treatments, the goal is to adopt healthy lifestyle habits so that the hair that is growing continues to multiply cells and lives longer. If, despite this, the hair does not improve or remains short, medical treatments should be used to improve the growth phase.”
At this point, Saceda stresses that the clinical approach is not usually limited to a single treatment. “We have oral medications, injections into the scalp and therapies with LED light and near-infrared. Where there is the most published evidence regarding lengthening the growth phase is with LED light,” concludes Dr. Saceda. These photoluminescent therapies are already applied in trichologists’ clinics. There are also at-home devices that help revitalize the scalp.
