Composition and role of the scalp microbiome:
A balanced and diverse microbiome is essential for maintaining a healthy scalp: it supports the skin’s barrier function, acts as protection against colonization by pathogens, and helps preserve the integrity of the skin (1,2).
The scalp microbiome is dominated by commensal bacteria and fungi, the most representative of which are: (1,3–5)
• Bacteria of the genus Cutibacterium: these anaerobic bacteria, particularly Cutibacterium acnes, play a role in regulating sebum and maintaining skin balance.
• Bacteria of the genus Staphylococcus: Staphylococcus epidermidis has beneficial effects, including protection against pathogens, while Staphylococcus aureus, found in higher proportions in certain scalp conditions, can become problematic.
• In terms of fungal commensals, Malassezia yeasts (particularly M. restricta and M. globosa) are very abundant on the scalp. These lipophilic fungi dominate the fungal flora of the scalp. They break down triglycerides from sebum into fatty acids, but if they become overrepresented or under specific conditions, they can cause inflammation and irritation of the scalp.
Scanning electron microscope images of a M. restricta biofilm produced by BYOME LABS
Dysbiosis of the scalp microbiome:
A disturbed scalp microbiome (dysbiosis) is clinically correlated with a sensitive scalp and is physiologically characterized by excess sebum. Overall, a disturbed balance of resident skin microorganisms is correlated with inflammatory disorders and skin infections (1).
• Cases Dandruff and seborrheic dermatitis
Dandruff and seborrheic dermatitis are part of the same disorder, which varies only in its location and severity. Dandruff is a common scalp condition affecting approximately 50% of the world’s population. It is characterized by itching and flaky skin with white or yellowish scales (8).
An excess of Malassezia spp. (particularly M. restricta) and the oxidation of squalene on the scalp have been linked to dandruff and seborrheic dermatitis. This is thought to be partly related to reactive oxygen species (ROS) produced by Malassezia spp., which can damage emerging hair follicles (1,8).
The impact of dysbiosis on the alteration of the epidermal barrier function, as well as on the triggering of inflammation, is not yet fully understood. However, it is accepted that restoring the skin’s microbial flora by increasing the amounts of protective microorganisms and reducing the amounts of potential pathogens can help rebuild the skin barrier (8).
• Cases of alopecia
Alopecia is common and can severely affect quality of life, both medically and psychologically. Its cause remains unknown. However, the condition of the scalp skin and hair quality are recognized as risk factors involved in its pathogenesis (5).
In a 2022 clinical study on the composition of the scalp microbiome in patients with alopecia areata, a significantly higher proportion of Corynebacterium species and a lower proportion of Staphylococcus species were observed in subjects with severe alopecia areata compared to healthy controls and subjects with mild forms of the condition (9). This is logical since the ecological niches conducive to the development of lipophilic microorganisms (Cutibacterium and Malassezia) are absent.
Factors influencing the scalp microbiome:
The balance of the scalp microbiome can be affected by a combination of factors. Intrinsic determinants (age, gender, diet, genetics) and extrinsic factors (pollution, UV radiation, cosmetics) modulate its composition (1).
BYOME LABS’ expertise:
We support cosmetic, dermo-cosmetic, and pharmaceutical brands with robust in vitro tests based on culturomics approaches to evaluate the effect of finished products and ingredients (all galenic forms) on microorganisms representative of the scalp microbiome. Nearly 20 years of expertise have enabled us to develop true mastery in the cultivation of demanding microorganisms.
We have developed specific culture media that now enable us to characterize Malassezia spp. in planktonic and biofilm conditions.
These models are particularly relevant for measuring the impact of your product on Malassezia spp. imbalances in scalp dysbiosis. Our models are based on the latest scientific data to design relevant contexts, including dandruff/seborrheic dermatitis, sensitive and unbalanced scalp, with artificial sebum addition.
What we deliver: clear results that provide scientific evidence for your claims (anti-dandruff and preserves scalp balance for example), whether demonstrating preventive or corrective action or the preservation of microbial homeostasis.
Our goal: to transform your promise into scientific evidence that can be used for both marketing and regulatory purposes.
Writers:
Stéphanie Badel-Berchoux
Laboratory Director
Margaux Jeanmougin
Marketing Director
Emma Trapeaux
Marketing project manager
Commercial CONTACT:
Discover Byome Labs’ full expertise in Clinical research here: https://www.skinobs.com/p/labo.php?id=324
Sources:
1.Townsend N, Hazan A, Dell’Acqua G. New Topicals to Support a Healthy Scalp While Preserving the Microbiome: A Report of Clinical and in Vitro Studies. J Clin Aesthetic Dermatol. oct 2023;16(10 Suppl 1):S4‑11.
2. Paul JK, Azmal M, Talukder OF, Haque ASNB, Meem M, Ghosh A. Unlocking the secrets of the hair microbiome: From scalp health to therapeutic advances. The Microbe. 1 juin 2025;7:100353.
3. Shah RR, Larrondo J, Dawson T, Mcmichael A. Scalp microbiome: a guide to better understanding scalp diseases and treatments. Arch Dermatol Res. 29 juill 2024;316(8):495.
4. Hu P, Henry J, Tiesman JP, Parlov M, Bacon R, Charbonneau D, et al. Scalp microbiome composition changes and pathway evaluations due to effective treatment with Piroctone Olamine shampoo. Int J Cosmet Sci. juin 2024;46(3):333‑47.
5. Mayer W, Weibel M, De Luca C, Ibragimova G, Trakhtman I, Kharaeva Z, et al. Biomolecules of Fermented Tropical Fruits and Fermenting Microbes as Regulators of Human Hair Loss, Hair Quality, and Scalp Microbiota. Biomolecules. 20 avr 2023;13(4):699.
6. Lousada MB, Edelkamp J, Lachnit T, Fehrholz M, Pastar I, Jimenez F, et al. Spatial Distribution and Functional Impact of Human Scalp Hair Follicle Microbiota. J Invest Dermatol. 1 juin 2024;144(6):1353-1367.e15.
7. Lousada MB, Edelkamp J, Lachnit T, Fehrholz M, Jimenez F, Paus R. Laser capture microdissection as a method for investigating the human hair follicle microbiome reveals region-specific differences in the bacteriome profile. BMC Res Notes. 6 mars 2023;16:29.
8. Mayser P, Genrich F, Meunier L, Nordzieke S. Scalp Microbiome and Dandruff—Exploring Novel Biobased Esters. Cosmetics. oct 2024;11(5):174.
9. Won EJ, Jang HH, Park H, Kim SJ. A Potential Predictive Role of the Scalp Microbiome Profiling in Patients with Alopecia Areata: Staphylococcus caprae, Corynebacterium, and Cutibacterium Species. Microorganisms. 21 avr 2022;10(5):864.
10. Fournière M, Latire T, Souak D, Feuilloley MGJ, Bedoux G. Staphylococcus epidermidis and Cutibacterium acnes: Two Major Sentinels of Skin Microbiota and the Influence of Cosmetics. Microorganisms. 7 nov 2020;8(11):1752.
