A review of Sisley’s new hair shedding serum and the science of scalp dysbiosis. Learn what the clinical data proves and how to evaluate microbiome claims.
On September 17, 2026, Paris Match Belgium published an interview with Sisley scientific research director José Ginestar. Ginestar has worked at the brand for 40 years. He detailed how Sisley collaborated with two private institutes and a university team to compare alopecic and non-alopecic scalp areas. This comprehensive research project ultimately led to the development of a new Super Sérum designed to target hair shedding.
A separate Harper's Bazaar UK article describes the Sisley research as a robust consortium lasting more than five years. The resulting product reflects a major shift in how the beauty industry approaches scalp health. Instead of looking only at the hair strand, researchers are now examining the complex microbial environment surrounding our hair follicles. The Sisley strategy aims to address both follicular activity and the delicate balance of scalp flora. Consumers are increasingly seeing products that incorporate language about inflammation and scalp ecology. However, it is essential to look closely at the data before changing your daily routine.
The central finding from the Sisley comparison was a distinct microbial imbalance in alopecic scalp areas. This specific biological imbalance is known as dysbiosis. According to Ginestar, the research team identified two bacterial strains that were consistently overrepresented in the areas affected by hair loss. Pauline Poussin is the scientific communication manager for Sisley. She called the role of scalp microbiota in hair loss the primary scientific breakthrough for the brand.
Poussin explained that Sisley associated these two bacterial strains with a low-level, chronic inflammatory state involving the hair follicle. This specific interpretation aligns with emerging biological data regarding scalp health and immune responses. A recent review summary describes the hair-follicle microbiome as potentially interacting with the immune system. Understanding this relationship provides vital context for how the scalp defends itself.
That same review summary cites an observed microbial shift in patients dealing with alopecia areata. This recorded shift included an increase in Propionibacterium acnes and a measurable decrease in Staphylococcus epidermidis compared to healthy controls. While these specific bacterial strains differ across various conditions, the data illustrates a clear pattern. Microbial environments fluctuate significantly during periods of active shedding, demonstrating that the scalp is a highly active biological ecosystem.
Ginestar stated that Sisley conducted more than 1,000 microbiological, preclinical, and clinical tests involving both women and men. He characterized the observed results relating to hair density, hairs per square centimeter, and overall hair health as very interesting. Harper's Bazaar cited three specific user-reported outcomes linked directly to the company.
According to those published reports, 76 percent of users noted reduced hair loss after using the formula. Another 73 percent reported a significant increase in overall hair density. Finally, 78 percent said their hair was noticeably less brittle.
While these percentages sound highly encouraging, consumers must separate user sentiment from rigorously validated clinical trials. These reported figures are not accompanied by crucial methodological details in the accessible coverage. We do not know the sample size, the control group, the exact follow-up duration, or the statistical analysis used to reach these numbers. Therefore, these statistics represent attributed product evidence rather than independently validated medical results. Objective hair-count measurements would provide a much clearer picture of efficacy.
The available information leaves several important scientific questions publicly unanswered. Neither accessible source identifies the two bacterial strains by name. The company has not published the full study protocol or provided an independently audited clinical dataset. Furthermore, dysbiosis is an observed imbalance rather than a confirmed root cause. It does not automatically prove that the bacteria caused the hair loss in the first place.
Medical reference material confirms that hair loss is not a single disease with one universal treatment. A microbial pattern observed in a condition like alopecia areata cannot automatically be applied to female-pattern hair loss or stress-related shedding. Ginestar himself listed hormonal factors, stress, and nutritional deficiencies as possible contributors to hair shedding in women. The interview also notes that cosmetic formulas are often completed several years before market launch, highlighting the long timelines involved in this research.
It is incredibly easy for consumers to feel overwhelmed by new clinical concepts and complex biological claims. I remember speaking with a dermatologist who told me her patients were coming in with severe anxiety about normal skin aging. That anxiety was driven entirely by social media filters and aggressive marketing. That conversation became a cornerstone of our philosophy. We decided right then that our publication would never frame natural changes like wrinkles or thinning hair as personal failures.
When cosmetic companies highlight a single biological factor like dysbiosis, readers must keep the larger medical picture in mind. A topical serum might support the superficial scalp environment effectively. However, it cannot replace thorough medical evaluation for complex autoimmune, hormonal, or genetic conditions.
Health-conscious women can use this information to make better choices about their daily routines right now. First, treat the scalp microbiome as a highly promising research direction rather than a standalone explanation for common shedding. If you experience sudden or persistent thinning, work with a clinician to understand the difference between hair shedding and hair loss.
If your doctor suspects a nutritional deficiency, address your diet before relying exclusively on topical cosmetics. Ginestar advised that a balanced diet is the first response when a nutritional deficiency is involved. Women evaluating topical options should ask whether product results rely on objective measurements or simple user surveys. You can read our framework on evaluating hair growth research to better navigate these distinctions in product marketing.
For specific scalp concerns, always consider whether standard medical treatments apply first. Medical references list specific interventions like glucocorticoid treatment for some conditions. They also strongly recommend eliminating physical traction where relevant. Understanding the numerous medical causes of hair loss in women is critical before purchasing a new microbiome serum. Proper care requires looking at the entire body system, rather than treating the scalp in isolation.
The cosmetic industry is actively expanding its scientific focus beyond the hair follicle alone. The Paris Match interview noted that Sisley is already working on another product planned for 2030. This suggests that the brand views hair and scalp science as a continuing research platform rather than a single launch.
Ginestar explained that truly personalized microbiome care would require deciphering the billions of microorganisms and combinations that differ between individuals. This biological complexity presents a massive challenge for researchers moving forward, as no two scalps are exactly alike.
This continuous innovation raises an important question for the future of healthy aging. Will tomorrow's hair longevity treatments require a complete sequencing of our individual scalp flora before we even select a targeted serum?
Stay connected for research and practical guidance on skin, hair, collagen, nutrition and beauty longevity. Clear ideas for people who want to understand how appearance changes with age and make better-informed choices over time.
Understand your skin, hair and body better without chasing every new trend, treatment or promise.
explore the Blog
