How we research, test and correct these guides
Every guide here follows four rules: a claim traces to a named source or to our own published method, tools show their inputs and formulas, limitations are stated rather than buried, and corrections are dated. This page explains that standard, including where we think the evidence is weak.
This is a store that sells rosemary oils, scalp combs and serums. That is a conflict of interest, and the honest response to a conflict of interest is disclosure and a standard, not a denial that it exists.
The four rules
- A source or a measurement, never a vibe. Health claims on this site cite a named study, a regulator or a clinical body. Where we give a number, we say where it came from and what it does not cover.
- Tools publish their method. Each calculator lists its inputs, the arithmetic behind the result and the assumptions underneath it, so you can disagree with the method rather than only with the output.
- We state the limits. If the evidence is thin, mixed or missing, the page says so in the section where it matters rather than in a footnote.
- Corrections are dated. When we change something substantive, the change and its date go on the page.
The rosemary oil test case
The clearest way to show the standard is to show it applied to the product we sell most of. Almost every rosemary oil claim in circulation traces to one 100-person trial published in 2015. It is a real trial and it produced a real result: rosemary oil and 2% minoxidil both increased hair count over six months, with no significant difference between them.
Here is what we do with that, and what we refuse to do with it:
| We say this | We do not say this |
|---|---|
| One trial found rosemary comparable to 2% minoxidil over six months | Rosemary oil is nature's minoxidil |
| The trial had no placebo arm, so the size of the effect is unknown | Rosemary oil is clinically proven |
| The comparator was 2% minoxidil, which 5% outperformed by 45% in a placebo-controlled trial | Rosemary is as effective as minoxidil |
| Rosemary is a documented cause of allergic contact dermatitis | Rosemary oil is natural, so it is safe for every scalp |
| Neither oil nor massage treats medical hair loss | Regrow your hairline in 30 days |
The result is a page that recommends rosemary oil as a low-cost scalp oil with a hopeful signal, and tells you plainly when the right answer is a clinician rather than a bottle. That is more useful than a page that oversells, and it is the page we would want to read.
You can see the same standard applied on the rosemary oil evidence page.
How the tools are built and checked
- We define the decision first, then find the inputs that actually change it. If an input does not move the output much, it does not go in the tool.
- The calculation is written as plain arithmetic with the constants stated in the page text, so the method is readable rather than hidden in an interface.
- Every calculator is run with at least two deliberately different input sets before publishing, and the outputs are checked for sense against the method description. The wash-day planner was run across a dry scalp and an oily scalp, a low-activity and a high-activity user, with and without oil treatment, to confirm the interval responds in the direction the reasoning predicts.
- Every quiz band is checked to cover the full score range, from zero to the maximum score, so no combination of answers can fall outside a result.
- Pages that change a recommendation link to the underlying source, so the reading is one click away rather than gated behind a summary.
What we will not do
| Not this | Why |
|---|---|
| Invent a statistic, or attribute one vaguely to unnamed studies | It is the fastest way to lose the reader and the search engine at the same time, and it is dishonest |
| Call a cosmetic product a treatment | Oils and serums change how hair looks and feels. Treatments for hair loss are a separate category with a separate evidence standard |
| Hide the commercial relationship | We sell these products, so the standard is disclosure rather than pretence |
| Cite a study we have not read | Every source listed on this site was checked for its actual finding, not for its headline |
| Give medical advice | We explain mechanism, evidence and safe use. Diagnosis and treatment belong to a clinician |
| Publish a page that could sit on any store unchanged | If a paragraph would read identically on a pet store site, it is not a specific enough paragraph |
How a guide gets written
- Start from the question people actually ask, from search result question boxes, support messages and returns data.
- Pull the primary sources on that question: randomised trials, systematic reviews, regulator guidance, professional body guidance and manufacturer specifications.
- Where a decision depends on a number, build the arithmetic into a tool rather than describing it in prose.
- Write the shortest version that answers the question, then add the detail that stops a bad purchase or a damaged scalp.
- Second pass specifically for overclaiming. Any sentence that asserts more than the cited source supports gets cut or softened before publishing.
Corrections and contact
If a page here is wrong, out of date, or cites something that has since changed, tell us and we will fix it and note the date at the top of the page. Reach us through the contact page.
Health guidance moves. The wash-frequency evidence on this site dates from 2021, the rosemary trial from 2015, and neither has been superseded by anything larger in the years since. When that changes, these pages change with it.
Start with these
Sources
- Panahi Y, Taghizadeh M, Marzony ET, Sahebkar A. Rosemary oil vs minoxidil 2% for the treatment of androgenetic alopecia: a randomized comparative trial. Skinmed 2015;13(1):15-21 — pubmed.ncbi.nlm.nih.gov/25842469/
- Olsen EA, Dunlap FE, Funicella T, et al. A randomized clinical trial of 5% topical minoxidil versus 2% topical minoxidil and placebo in the treatment of androgenetic alopecia in men. J Am Acad Dermatol 2002;47(3):377-385 — pubmed.ncbi.nlm.nih.gov/12196747/
- Punyani S, Tosti A, Hordinsky M, Yeomans D, Schwartz J. The impact of shampoo wash frequency on scalp and hair conditions. Skin Appendage Disord 2021;7(3):183-193 — pmc.ncbi.nlm.nih.gov/articles/PMC8138261/
- Hessefort YZ, Holland BT, Cloud RW. True porosity measurement of hair: a new way to study hair damage mechanisms. J Cosmet Sci 2008;59(4):303-315 — pubmed.ncbi.nlm.nih.gov/18818850
- NHS. Hair loss: causes and treatment — www.nhs.uk/conditions/hair-loss
- American Academy of Dermatology. Hair loss resource center — www.aad.org/public/diseases/hair-loss