A scalp shampoo study published in 2025 tracked changes in microbes and surface fats in 30 adults over 12 weeks. Researchers reported differences after use of a specific shampoo formula. The small study adds human data, but cannot show which ingredient caused each change or predict results from another product.
Source checked: September 16, 2026. The paper appeared online on May 21, 2025, in the International Journal of Cosmetic Science. The experiments took place in 2022. Publication date and study date are different facts; this is recent reporting of earlier work, not a trial run this year.
- The study enrolled 30 adults aged 18 to 60.
- Each study group contained 15 people.
- The test shampoo contained both caffeine and adenosine.
- Scalp samples were taken at baseline and at week 12.
- The authors said causal links between microbes and lipids remain unresolved.
What did the scalp shampoo study actually test?
Li and colleagues tested a shampoo containing 0.4% caffeine and 0.2% adenosine against a control shampoo without those two ingredients. Participants were assigned to groups at random. This was a single-blind study, meaning one side of the study was kept unaware of group assignment. It was not a test of every shampoo containing either ingredient.
All participants first used the control shampoo for a two-week preparation period. The team then recommended washing four times a week for 12 weeks. That shared schedule helped define the conditions being studied. It does not set a wash schedule for everyone reading the paper.
What do microbiome and lipidome mean here?
The scalp microbiome refers to the community of microbes found on the scalp. The lipidome is the collection of fats, called lipids, detected in a sample. In this study, researchers used swabs and lab tools to describe both. These measurements are different from a person's report that their roots look oily or their hair feels clean.
Samples came from four scalp regions. Participants were asked not to wash for two days before sampling. Keeping that interval consistent matters: a sample taken just after rinsing is not the same kind of snapshot as one taken two days later. The collection method is part of the result, not a footnote to ignore.
What changes did the researchers report?
The authors reported changes in several groups of microbes and in several lipids after use of the test shampoo. They also found statistical links between some microbial and lipid measurements. Those links describe patterns in the collected samples. They do not establish that a particular microbe caused a lipid change, or that changing one would produce a visible benefit.
The paper also includes hair measurements. This explainer focuses on the scalp-sampling work and its limits, not on turning those measurements into cosmetic claims. A research team can ask several questions in one paper. A reader still needs to check each answer separately, using the methods that support it.
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Where does this sit among evidence stages?
This paper offers a small human comparison study, rather than a cell experiment or an animal model. That distinction matters because actual people used the shampoo. Yet the size, duration, formula, and participant mix still limit its reach. The table compares kinds of evidence, not how well products perform or which product someone should choose.
| Evidence stage | What is observed | Main boundary |
|---|---|---|
| Laboratory or animal research | Cells, tissue, or animals under set conditions | Does not establish an outcome in human use |
| This 30-person human study | Two shampoo groups over 12 weeks | Small sample and one combined formula |
| Larger independent human studies | Whether a finding repeats across more people and settings | Still applies only to the products and outcomes actually studied |
A longer study is not automatically a better study. Clear methods, suitable comparisons, and complete reporting matter too. The useful question is whether the evidence fits the claim being made. A paper about one formula cannot carry the burden of proving a different jar on a shelf.
What do these results not tell you?
What these results do not tell you: the study cannot separate the effects of the two named ingredients because they were included together. It also cannot establish a lasting change beyond the follow-up period. With 27 women and three men enrolled, the findings should not be assumed to describe all groups equally well.
The authors themselves note the small sample and uneven sex distribution. They also explain that their sequencing approach has limits when used to infer what microbes do. Detecting a microbial pattern is not the same as watching its function. A proposed explanation remains a question for future work until it is tested directly.
Why should readers check who supplied the shampoo?
Readers should check product supply, author affiliations, and funding because these give useful context for a study's design. This paper lists both university and biotechnology-company affiliations. Its methods name a company that supplied the test shampoo. These details do not invalidate the results, but they make independent repetition a useful next step.
The paper reports support from the China Postdoctoral Science Foundation and states that the authors declare no conflicts of interest. Read that statement alongside the affiliations and methods, not in place of them. Neither a company connection nor a university name decides whether a finding holds up. The evidence has to do that work.
What should this mean for a scalp-care routine?
This study is a reason to read formula-specific claims closely, not a reason to copy a research schedule. Follow the directions on the product you actually have. A rinse-off shampoo and a leave-on gel differ in use and contact time. Shared ingredient names do not make them interchangeable or transfer findings from one to the other.
Deoxylocks is a physician-formulated cosmetic hair-care product. This shampoo study does not establish results for Deoxylocks. Keep ingredient research background separate from current product details and directions. Knowing where evidence stops is useful, even when the headline sounds more decisive.
What else do readers ask about scalp shampoo studies?
The most useful follow-up questions concern size, timing, formulas, and what the measurements mean. A source can be recent without being large, and a human study can still leave important questions open. These short answers keep those distinctions separate so the study is easier to read without turning it into a shopping recommendation.
Was this a human study or an animal study?
It was a human study involving 30 adults, with 15 people in each group. That makes it different from animal research, but the small sample still limits how broadly its findings can be applied.
Did the researchers test caffeine on its own?
No. The test shampoo contained both caffeine and adenosine. Without separate groups for each ingredient, the study cannot say how much either one contributed to a reported difference.
Does a microbiome change always mean a benefit?
No. A difference in a lab sample is not automatically a useful change for the person. Researchers need to establish what changed, whether the pattern repeats, and how it relates to a meaningful outcome.
Was the study conducted in 2025?
No. The paper was published online in May 2025, but its methods date the study to 2022. Checking both dates helps distinguish recent publication from newly collected data.
Can I apply the findings to another shampoo?
Not directly. Formulas, ingredient amounts, use schedules, and participants can differ. Look for evidence on the actual product and claim, not just a familiar ingredient in a paper's title.
Sources
Primary sources for the figures in this article. Registry records were checked on 15 August 2026.
Deoxylocks 5% 2DDR Scalp Hydrogel
A physician-formulated cosmetic hydrogel for nightly scalp care. Non-hormonal, clear and odorless, applied once daily to the scalp. Backed by a 90-day risk-free return policy.
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