“The classic corneometer reading is no longer sufficient on its own to tell the full story.”
Anne Charpentier, CEO & Founder, Skinobs
Hydration is the most universally sought cosmetic benefit. It crosses every geography, every skin type and every product category. Yet in 2026, the way hydration is measured and substantiated has changed considerably. Consumers expect deeper, longer-lasting, more structural action. Regulatory reviewers expect multi-method dossiers and mechanistically supported claims. And the testing toolkit keeps expanding, from surface measurements to real-time cellular imaging.
This white paper maps that landscape. It draws on Skinobs platform data and on the latest advances in skin biology, biometrology and clinical study design.
What the Skinobs data shows
Between January and May 2026, hydration-related searches on the platform generated 480 clinical queries, involving 85 devices from 36 manufacturers, across 208 providers in 45 countries. On the preclinical side, 19 additional searches targeted biomarkers, mainly hyaluronic acid. Hydration is the most active research area on the platform. Three signals stand out:
- Demand for depth is growing. The most searched devices (18 searches each) probe the viable epidermis and dermis: MoistureMeterEpiD, MoistureMeterD, dermo-spectroscopy systems. Classic stratum corneum instruments such as the Corneometer or the MoistureMeterSC follow closely with 13 searches each.
- Hydration and skin structure are converging. Collagen and elastin measurement devices (SIAScope, DermaLab Skinlab Ultrasound, RSOM Explorer C50, confocal microscopy, K-Probe XPolar) were each searched 12 times within hydration queries. The brief is no longer “prove that my product hydrates” but “prove that it hydrates, strengthens and improves skin structure over time”.
- A global ecosystem. Hydration profiles, consumer expectations and regulatory requirements vary from one country to another. A study designed for a European panel does not automatically transfer to a Korean, Brazilian or North American context.
The biology of hydration: from surface to dermis
Hydration is not a single parameter. It results from interconnected mechanisms spread across several levels of the skin, each with its own physiology and its own measurement logic.
- Stratum corneum: its lipid matrix (ceramides, free fatty acids, cholesterol) limits passive water loss to 5 to 15 g/m²/h under normal conditions. Inside the corneocytes, the natural moisturizing factor (NMF) binds water and keeps the stratum corneum flexible.
- Viable epidermis: aquaporin-3 (AQP3) channels facilitate water and glycerol transport. Their expression is an emerging mechanistic endpoint in advanced in vitro and ex vivo studies.
- Dermis: hyaluronic acid, able to retain up to 1,000 times its weight in water, is organized within the collagen and elastin network. Its content declines significantly from the fourth decade of life.
The science has also moved well beyond the classical barrier-and-NMF model. The microbiome, the hormonal environment and the exposome explain why the same product can perform very differently depending on the biological profile of the panel. Post-menopausal skin, for example, is drier, thinner and slower to recover from barrier perturbation, which calls for adapted inclusion criteria, longer study durations and measurement batteries that combine surface and structural endpoints.
Measurement methods for every level
No single method can characterize a formula’s hydrating action across all levels of the skin. The most credible dossiers combine instruments at several depths.
- Stratum corneum and barrier: corneometry (Corneometer CM 825) has been the reference for over three decades and remains the most widely accepted primary endpoint for surface hydration claims, but it only measures the outermost micrometres of the stratum corneum. TEWL measurement (Tewameter TM 300, Aquaflux AF200) informs on barrier integrity.
- Epidermis and dermis: impedance spectroscopy (MoistureMeter range, Epsilon E100), infrared spectroscopy, confocal Raman spectroscopy (the only non-invasive method able to quantify NMF in situ), ultrasound and spectrophotometry (SIAScope) reach the deeper layers.
- Emerging technologies: LC-OCT produces real-time, three-dimensional images of skin microstructure at cellular resolution. Multiphoton tomography visualizes collagen and elastin fibres in the living dermis.
- Preclinical: hyaluronic acid, AQP3 expression, filaggrin and ceramide synthesis on reconstructed epidermis and 3D skin models, complemented by in silico modelling. The platform references 77 preclinical providers across 15 countries.
- Connected diagnostics: smartphone-compatible probes, smart patches and portable sensors open the way to home-use studies with larger and more diverse panels. Their integration into regulatory-grade dossiers remains a methodological frontier.
A few benchmarks to choose according to the targeted claim:
| Claim | Primary method | Complementary method |
|---|---|---|
| Moisturizing | Corneometry, impedance, capacitance | Dermoscopy, 3D imaging |
| Anti-dryness | TEWL | Lipid composition, surface imaging |
| Lasting hydration | Near-infrared spectroscopy | Microtopography, Raman |
| Deep hydration | Ultrasound, RSOM, OTTER | SIAScope |
| Architecture & structure | LC-OCT, MPT, confocal Raman | Lipid composition |
| Well-ageing, density | LC-OCT, MPT | Impedance, ultrasound |
| Molecular level | Raman, LC-OCT | AQP3 expression in vitro |
Designing a robust in vivo study
The best instruments will not save a poorly designed study. In hydration testing, the most common cause of unusable data is not the instrument but the protocol: a panel that does not reflect the target population, a sample size that was never statistically powered, environmental conditions that drift between visits, or time points chosen by habit rather than by the claim being tested. The white paper details the key points of attention:
- Start with the claim. An “instant hydration” claim requires a different panel, different measurement points and different instruments than a “clinically proven improvement in skin dryness in 4 weeks”.
- Design the panel carefully. Corneometry threshold at inclusion (generally below 35 arbitrary units on the forearm for dry skin, between 35 and 55 for normal skin), sample size calculated by a biostatistician before recruitment, and a washout period before baseline measurements.
- Control measurement conditions. Temperature between 20 and 22°C, relative humidity between 40 and 60%, 20 to 30 minutes of acclimatization, the same technician and the same site throughout the study.
- Choose time points according to the targeted effect. From 30 minutes to 4 hours for an immediate effect, up to 8 or even 24 hours for a single-application effect, and weekly or bi-weekly measurements over 28 to 56 days for a deep or structural effect.
- Combine methods. Multimodal studies, pairing the stratum corneum with deeper layers and in vitro biomarkers, significantly strengthen the scientific credibility of a dossier, especially for premium products.
Finding the right laboratory
A well-designed protocol produces unreliable data if it is run by a laboratory without the right instruments, trained operators or suitable panel recruitment. The Skinobs platform connects formulators and R&D teams with specialized laboratories in 124 countries, searchable by measurement method, skin type, study design and geographic zone.
Download the free white paper
Whether you are designing your first hydration study or reconsidering your evaluation approach, this white paper is intended as both a scientific reference and a practical decision framework.
Need a laboratory for your hydration study? Find your test and laboratories on the Skinobs platform.
