Did you know that the phrase "snake oil" actually has a real origin story, and it's a fitting way to start this article.
In the 1800s, Chinese railroad workers in the U.S. used genuine Chinese water snake oil, which is actually rich in omega-3 fatty acids, to treat joint pain, which was moderately successful[1]. American entrepreneurs quickly took notice and started selling their own "snake oil" tonics, but cut every corner to reduce costs and increase profit: less snake oil, more mineral oil, and of course, zero evidence. When one of the most famous brands, Clark Stanley's Snake Oil Liniment, was finally tested by federal regulators in 1917, it contained no snake oil at all. The term became permanent shorthand for a product that promises everything and delivers next to nothing.
More than a century later, the hair care aisle has a version of the same problem - not because every product is a scam, but because the entire category isn't required to prove anything before it reaches your social media feed or your local Sephora.
Cosmetics vs. Drugs
To understand why this is, we must first review the role of the FDA, the nation's oldest comprehensive consumer protection agency. In the U.S., the FDA classifies products by the claims on the label, not by how they're marketed. Under the Food, Drug, and Cosmetic Act, a product is a drug if it claims to treat, mitigate, prevent, or cure a disease, or affect the structure or function of the body. A product is a cosmetic if it's intended only to cleanse, beautify, or alter appearance.[2]
That's precisely why hair serum packaging uses careful language, like "improves the look of fuller, thicker-looking hair" instead of "regrows hair." Drugs like minoxidil (over the counter; OTC) and finasteride (prescription) are actually re-purposed drugs, meaning clinical trials were performed using them for different medical indications (e.g., hypertension, minoxidil; prostate cancer, finasteride) and hair growth was observed as a side effect. To date, there have been zero FDA-approved drugs developed specifically for hair loss treatment. Cosmetics, including most "serums," "boosters," and "activators", don't need pre-market approval and don't have to prove they work, as long as they stay in cosmetic-only language [3].
Now, this doesn't mean cosmetics are unsafe or that the category is a free-for-all - ingredient restrictions and general manufacturing standards still apply. What it means is that efficacy, and importantly, testing for efficacy, is not really anyone’s job.
Therefore, the burden falls to you.
5 things to look for in a hair serum that’s tested as if it were regulated
Since the regulatory bar is low, here's what actually separates a serum worth considering from one that's coasting on marketing language. Most products on the market check maybe one of these five boxes, if that. So alongside each one, we're including how our Dual-Path Hair Revival Serum measures up, since it's one of the few examples that's publicly documented enough to actually check.
1. Named, independently researched active ingredients
Skip anything hiding behind a vague "proprietary blend" with no ingredient names or amounts. Look for active ingredients that have published research behind them. For example, Capixyl (a red clover extract and biomimetic peptide studied for inhibiting 5-alpha-reductase), Redensyl, Procapil, and caffeine all have independent literature to varying degrees. Since the actual clinical data is thin, treat this as encouragement, not proof - sample sizes in this literature are unfortunately concerningly small. Look for ingredients with registered INCI-names[4]. Developed by the International Nomenclature Committee (INC) - INCI-names are systematic names internationally recognized to identify cosmetic ingredients.
RE:YOU's Dual-Path Hair Revival Serum features a proprietary technology called NOVOGRO™ (three molecules: NOVOGRO™-273, -623, and -624). These new ingredients and other actives are registered with INCI as well.
2. Credible science behind the mechanism, not just the marketing
Beyond ingredient names, look for an actual explanation of why something should work - tied to real biology (e.g., hair follicle stem cells, dermal papilla health, blood flow to the scalp) and ideally referenced to peer-reviewed or at least publicly available research, rather than adjectives like "activating" and "revitalizing" doing all the work.
At RE:YOU, we published our reasoning and approach: NOVOGRO™-623 and -624 support dermal papilla cell health, while NOVOGRO™-273 activates a pro-regenerative pathway (HIF-1α activation via PHD2 inhibition) linked to blood vessel growth and nutrient delivery to the scalp. The manuscript is available as a bioRxiv preprint, and is currently under revision at a scientific journal.
The research and development team behind RE:YOU is highly interdisciplinary, with scientists trained at Princeton, Harvard, Caltech, and Northwestern across biology, engineering, medicinal chemistry, physiology, and more. Altogether, the team has published dozens of high-impact publications, including in Nature and Nature Biotechnology, and is well-respected in the field.
3. Testing against an active comparator, not just a placebo or itself
Most clinical studies of hair serums - when they exist at all - compare the product to a placebo, or just show before-and-after photos of people using the product with nothing to compare against. Both designs are limited because hair growth is slow, cyclical, and easily influenced by many factors so a product can look effective simply because time passed or the participants were hopeful. Beating a placebo shows a product does something. But it doesn't tell you whether that something is worth choosing over what already exists.
A head-to-head against an established treatment (like minoxidil) is being held to a much higher standard, since the serum has to perform better than something that already works.
How to verify it: look for the registered trial on ClinicalTrials.gov. Any serious clinical trial should be publicly registered on ClinicalTrials.gov, a free database run by the U.S. National Library of Medicine. Search the brand or product name, or the trial's registration number (it begins with "NCT"). A registry entry lets you check, independently of the brand's marketing, the details that matter most:
- The comparator: placebo, no treatment, or an active treatment like minoxidil.
- The planned size and design: how many participants, how they were assigned, exclusions, and how long the study runs.
- The pre-specified outcomes: what the researchers said they would measure before seeing results.
- The status and dates: whether the study is ongoing, completed, or stopped early.
If a brand says "clinically proven" but can't point you to a registration number, that's concerning.
RE:YOU is running a 190-participant trial testing the Dual-Path Hair Revival Serum head-to-head against an OTC minoxidil product, explicitly choosing that harder comparison over a placebo. The trial is registered on ClinicalTrials.gov under identifier NCT07785869, so you can check the design, comparator, and planned outcomes yourself rather than taking our word for it.
4. Objective, machine-measured results, not just photos or surveys
Before-and-after photos are vulnerable to lighting, angle, and styling. Self-reported surveys are vulnerable to expectation and recall bias. Real evidence includes objective measurement: digital phototrichograms (magnified scalp imaging that counts and measures individual hairs), standardized shedding tests (like a controlled comb test), or clinical grading against a standardized scale - ideally more than one of these used together, and ideally anchored to a fixed reference point on the scalp so measurements are comparable over time.
NCT07785869 included all three types of objective measurement. For a portion of participants, a tattooed micro-reference point marked a fixed spot on the scalp, allowing digital phototrichogram imaging to count and measure hairs at that exact location over time. The study also used a standardized comb test to measure shedding and independent clinical grader scoring - in addition to, not instead of, participant self-reports.
5. Independent conduct and transparency about limitations
A trial run and analyzed completely by the brand itself, with an undefined methodology, is worth less than one conducted by an independent lab with a predefined statistical plan, institutional review board (IRB) oversight, and public registration (e.g.,, on ClinicalTrials.gov). Equally important: does the brand disclose what their data doesn't yet show - interim results, ongoing follow-up, or limitations - or only the flattering numbers?
NCT07785869 was conducted by an independent clinical research lab (Eurofins) rather than by RE:YOU, and used a predefined statistical analysis plan with IRB oversight. Currently, the 90-day interim data from an ongoing 6-month study are available, with final results still pending.
The Bottom Line
The main issue here isn't that hair serums are inherently ineffective - it's that the category isn't required to prove anything before it's sold, which means the burden of evaluation sits with you, not a regulator. Most products in this space won't clear more than one or two of the five criteria above. When one clears all five - independent trial conduct, an active comparator, objective machine measurement, transparent limitations, and researched active ingredients - that's a meaningfully different claim than "clinically proven" marketing usually represents, even if it still falls short of drug-level proof.
FAQ
- Are all hair serums unregulated? Most are, if marketed as cosmetics. A serum containing an active drug ingredient like minoxidil, disclosed on a Drug Facts panel, is regulated as an OTC drug instead.
- Does "unregulated" mean unsafe? No - cosmetics still meet general safety and labeling standards. It means efficacy claims aren't independently verified before sale.
- What's the single best sign a serum's evidence is credible? Testing against an active comparator (like minoxidil) with objective, machine-measured endpoints - rather than a placebo, photos, or self-report alone.
*This article is for informational purposes only and isn't medical advice. Consult a healthcare professional about your specific situation.
