A 12-week study in the Journal of Cosmetic Dermatology tracked what a scalp serum actually does to the microorganisms living on the scalp. Uyen Thy Nguyen and six co-authors, including researchers affiliated with the serum's formulator, enrolled 56 participants and sequenced bacterial and fungal DNA from scalp swabs at baseline, 4 weeks, and 12 weeks.
The method matters here. The team used 16S rRNA sequencing for bacteria and ITS2 sequencing for fungi, the standard pair for profiling a skin microbiome without culturing organisms in a lab. Alongside the sequencing, they measured scalp thickness, oiliness, moisture, and pH with instrument readings, giving the microbial data physiological numbers to sit next to.
The headline result is a ratio: bacterial load relative to fungal load rose significantly at both 4 and 12 weeks compared to baseline. The authors attribute that shift mainly to bacteria increasing, not fungi declining. Fungal diversity, measured by the Shannon index, also went up over the same period, so more fungal species were present and more evenly represented, even as bacteria pulled ahead in sheer numbers.
Two named organisms carry the paper's specific claims. Cutibacterium namnetense, a bacterial species, increased significantly in abundance by week 12. Cladosporium sp., a fungal genus common on skin and in indoor air, did too. The paper also reports a negative correlation between Malassezia sympodialis, a yeast linked to dandruff and seborrheic dermatitis in other research, and scalp thickness: as that yeast's abundance went down, scalp thickness tended to go up.
What the abstract doesn't supply is a mechanism linking any single ingredient in the serum to these shifts. The study tested a finished product, not its components in isolation, so the sequencing data show that the scalp community changed under use and don't show which molecule in the formula drove Cutibacterium namnetense up or Malassezia sympodialis down. The authors' own conclusion stays in that range, stating that the treatment 'may support scalp health by respecting the balance of the scalp microbiome,' phrasing that describes a correlation the data support rather than a mechanism the data establish.
The correlation between pH, hydration, and microbial composition that the paper mentions stayed statistically nonsignificant. That's a detail easy to lose in a press summary built around the headline bacteria-to-fungi ratio, but it's the line separating what this paper demonstrates from what a marketing claim built on it might imply. The 56-person, 12-week design establishes that a measurable microbial shift occurred under this product. It doesn't establish that shift as the cause of any visible change in scalp condition, and the paper doesn't claim otherwise.
