In-vitro vs in-vivo skincare testing: What do these claims actually mean?

There was a time when choosing skincare meant checking the ingredients, the texture, and perhaps whether it fits into your beauty routine. But as our knowledge of beauty evolves, so do the claims. Clinically proven, dermatologically tested, and very recently, the in-vivo, in-vitro battle—these terms can make a product sound reassuringly scientific, but they don’t all mean the same thing. And that distinction matters.

“The most honest way I can explain in-vitro and invivo testing is this: in-vitro tells you what an ingredient can do under controlled, almost protected conditions; in-vivo tells you what survives contact with real skin, real behaviour, and real formulation complexity,” says Prachi Bhandari, Co-founder and Head of Research and Development at Aminu. “Both matter, but they do not mean the same thing.”

IN THE LABORATORY 

In-vitro involves testing outside the body. An ingredient may be studied on cells, tissues, a reconstructed skin model or on another biological system. It allows researchers to isolate a particular mechanism and investigate whether an ingredient can, for instance, influence collagen activity, reduce oxidative stress, or affect pigmentation.

The controlled nature of laboratory testing is both its strength and its limitation. Results can depend on the model used, concentration, pH, exposure time, temperature, and sample preparation. In-vitro data can establish biological potential, but it cannot necessarily predict how an ingredient will behave once it is incorporated into a finished formula and applied to skin.

“From a dermatologist’s perspective, in-vitro-only evidence should usually be treated as preliminary, not definitive,” says Dr Jaishree Sharad, cosmetic dermatologist and Founder of Skinfinitii Aesthetic Skin and Laser Clinic. Dr Kiran Sethi, Medical Director and Founder of ISYA Aesthetics, says this is one of the fundamental limitations of translating laboratory findings into real-world skincare. “An invitro study proves an ingredient has the potential to trigger a cellular signal, but not that it will survive topical application to do so,” says Dr Sethi. In other words, in-vitro data is valuable, but isn’t the final truth.

ONTO THE SKIN 

On the contrary, in-vivo means testing on a living organism. In skincare, this can mean testing a product on human volunteers and measuring what happens to their skin. But it’s far more measured, rather than relying solely on whether someone thinks their skin looks better. This form of testing is integral, as your skin isn’t just a collection of cells sitting in a laboratory. “Human skin is more complex than a lab model,” explains Dr Sharad. Real skin has a barrier that changes over time, blood flow, sweat and oil production, hair follicles, and an immune system—all of which can affect how an ingredient behaves.

Bhandari adds that real-world factors can make a difference too—skin barrier strength, microbiome, pigmentation tendencies, hormones, weather exposure, and even how consistently someone uses the product. Even location of testing matters. “Forearm skin is not exactly facial skin,” she points out. A controlled patch is not equivalent to incorporating a product into a daily facial routine, just as a 28-day result does not necessarily tell us what will happen after three months. But all of these do not make human testing unreliable. It simply means that studies have to account for the fact that humans are human.

FINISHED FORMULA 

There’s a difference between testing an ingredient and a product. Consider a serum formulated with niacinamide, for example. While there may be substantial research supporting the benefits of niacinamide for the skin, but that does not necessarily establish that the specific serum, at its particular concentration and formulation, will deliver the same results. The rest of the formula—concentration, delivery system, stability, pH, and the interaction between ingredients—will influence performance.

“Consumers shouldn’t have to reverse-engineer a brand’s testing strategy,” says Rachna Bahadur, Founder and CEO of Flout Beauty. “It is the brand and their formulator’s job.” For Bahadur, testing the finished formula is ultimately about ensuring that the claim belongs to the product being sold, rather than borrowing credibility from research conducted on an individual ingredient.

That distinction becomes particularly relevant when brands use sophisticated language to describe relatively straightforward evidence. A product containing a well-researched active is not automatically a clinically proven product. But here’s the caveat—one is not superior to the other. “The strongest evidence is usually well-designed clinical trials on the finished product,” says Dr Sharad. For consumers, that is ultimately the most relevant question—whether the product produces a measurable result when used as directed.

BEYOND THE JARGONS 

Bahadur is particularly blunt about the industry’s appetite for scientific-sounding claims. “Pretentious and performative science is the main problem.” The issue isn’t that testing is unnecessary. It is that different types of evidence are sometimes presented as though they carry the same weight.

Clinically proven does not, by itself, tell you the size or duration of a study, whether there was a control group or what was actually measured. Lab-tested tells you even less. And dermatologically tested should not automatically be interpreted as dermatologist-approved.

“The biggest crime is when something is twisted to play on people’s insecurities,” she says. “For example, a well-respected brand writes ‘9X% brighter skin’. ‘Brighter’ or more even skin can be a legitimate measure of skin health. But in a non-native English-speaking market with so much baggage around fairness and the Fitzpatrick scale, the language gets complicated.” The main question to ask would be: will the product actually change your natural skin colour? If you read the fine print, you may find 9X% of users said their skin looked brighter.

“Those are very different claims. In reality, you only know that some users noticed a change—you don’t know how much, or whether it was objectively measured. The claim has changed the lens through which you see the product. And that’s precisely where the gap between marketing language and evidence matters.”

The next time a product promises clinical results, experts recommend looking beyond the terminology. Was the finished formula tested, or was it just an ingredient? What was actually measured, in how many people, and for how long? Who was tested, and what kind of evidence supports the claim?

Consumer feedback, in vitro data, and clinical results are not interchangeable. Simply put, don’t ask whether a product has been tested, but whether the evidence actually matches the claims.

Image: Courtesy Getty Images

This article originally appeared in Harper's Bazaar India's October 2026 print issue.

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