This is Part 2 of our three-part series on skin health as an overlooked research tool.

‍Part 1 of our skin health series made the case for treating skin as more than a cosmetic concern. As the body's largest organ, skin can provide information about biological age, inflammation, metabolic function, immune activity, and hormonal balance well beyond the boundaries of dermatology. That raises a practical question this post takes on: how does skin health actually get measured, in the dermatology office and beyond it?

This article covers methods used in site-based and decentralized clinical and research settings. Part 3 will explain how to add skin health endpoints to your study on Alethios.

How Skin Health Is Measured Onsite

Skin is right in front of us, but measuring it isn't always straightforward. Clinicians and researchers use several complementary methods to evaluate skin appearance, structure, function, and health.

On the Surface

In many cases, changes in skin health can be observed directly through differences in appearance or texture. For example, sun exposure may cause tanning, freckles, redness, or peeling. Although it may seem simple, visual examination is a valuable measurement method that allows clinicians to document skin characteristics and track changes over time.

However, not all skin changes are readily visible or have an obvious cause and some clinically important features are difficult to evaluate with the naked eye. That is where dermoscopy comes in. Using a handheld magnifying device with specialized lighting, clinicians can examine colors and structures within the skin that may not be visible during a standard visual examination. When used by trained clinicians, dermoscopy can improve the diagnostic accuracy of assessments of suspected of melanoma compared with visual inspection alone (Cochrane review of dermoscopy versus visual inspection for melanoma).

Measuring Hydration and Barrier Function

While visual inspection is useful, it cannot fully capture how the skin barrier is functioning. However, researchers have other methods to measure skin health quantitatively. One method, corneometry, approximates the hydration in the stratum corneum—the outermost layer of skin—by reading the skin's electrical capacitance, the ability to store electric charge. Corneometry involves sending a low-level, safe electrical field into the top layer of skin, which changes based on how much water is present. Since water affects the skin’s electrical properties, higher readings on the device generally indicate greater hydration.

While corneometry measures how much water is in the skin, transepidermal water loss (TEWL) testing uses a device to measure how much water is escaping through the skin barrier. Higher TEWL can indicate reduced barrier integrity and issues with skin barrier function.

Together, corneometry and TEWL offer complementary information—how much water is near the skin surface, and how much is lost through the skin barrier— that is widely used in dermatology and skincare research (TEWL and hydration assessment of stratum corneum function; TEWL-hydration ratio in atopic dermatitis).

Quantifying Elasticity and Color

Researchers can also quantify physical characteristics that might otherwise be assessed visually. Cutometry measures the skin’s ability to stretch or deform and then return to its original position, providing insight into the skin’s elasticity. The method uses gentle, controlled suction to calculate standardized measures of skin elasticity and firmness, which are commonly used in scar, skin care, aging, and longevity research.

Device-based color measurements can quantify skin pigmentation and redness. Instruments like the Mexameter use reflected light to calculate melanin and erythema. Color measurements provide a standardized alternative to visual scoring and can help track changes in pigmentation more reliably (objective color measurement device comparison, PubMed).

Seeing Under the Surface, From Above

Optical coherence tomography, or OCT, extends skin imaging below the visible surface by using reflected light to produce real-time, cross-sectional images of skin structures. In dermatology research and selected clinical applications, OCT can help characterize and monitor structural changes without removing tissue. (OCT clinical applications review, PubMed).

Biopsies and Looking Under the Surface

When noninvasive methods cannot establish or confirm skin health factors, a clinician may perform a skin biopsy—a minimally invasive procedure in which a small piece of skin is removed and examined closely. Unlike the methods explained above, evaluating skin microscopically offers direct insight into skin cells and tissue structure. 

Decentralized Skin Health Measurements

Onsite methods can provide detailed and clinically valuable information, but most only capture skin at a particular moment. Recording a trend would require repeated clinic visits which may be costly for researchers and burdensome for participants.

Remote and decentralized methods can allow researchers to collect measurements more frequently and from a broader participant population. Their suitability depends on the endpoint, the device, and how well the method has been validated.

Wearables and Continuous Monitoring

Existing and emerging wearable sensors can track measures such as skin temperature, sweat composition, and hydration-related signals over time (wearable hydration-monitoring review, JMIR mHealth; wearable biosensor hydration monitoring, npj Digital Medicine). Instead of relying on a single office measurement, these devices allow researchers to observe changes across daily activities, environmental conditions, or study interventions. The amount of data provided through wearables can reveal patterns and trends that isolated measurements might miss (review of wearable hydration monitoring; wearable biosensor study).

Microbiome Assessments

Skin health also involves communities of bacteria, fungi, viruses, and other microorganisms living on and within the skin. Researchers increasingly study these microbial communities in relation to conditions such as acne, atopic dermatitis, and impaired barrier function.

Some microbiome evaluations can use at-home test kits so participants can collect samples at home and send them to a laboratory for sequencing. Remote collection offers convenience for participants and makes geographically diverse studies easier to conduct than setting up multiple site locations (skin microbiome techniques review, PMC).

Digital Endpoints

Some decentralized assessments don’t require any physical sampling and instead use a phone. Smartphone-based, AI-powered platforms use standardized photographs and image-analysis models to estimate visible features such as wrinkles, redness, pigmentation, and texture.

Platforms such as Haut.AI are designed to support standardized image capture and automated scoring across large participant groups (overview of the Haut.AI clinical studies platform). Beiersdorf’s Skinly research initiative has also explored app-based imaging in combination with conventional dermatological assessments (Beiersdorf’s Skinly study).

"Skin endpoints such as structural aging signs and pigmentation have been difficult to measure reproducibly. Two graders can score the same skin differently, and so can the same grader on two different days, and that variability can obscure a real product effect. Our models hold ICC 0.97 to 0.98 across five facial endpoints in validation, whether the image comes from a clinical camera or a participant's own phone at home. Working with the Alethios team, we have made that measurement available inside their research platform. It does not replace the expertise around the study; it gives that expertise something reproducible to build on."

— Anastasia Georgievskaya, CEO & Co-Founder, Haut.AI.

Two Layers, One Measurement: AI Models and Dermatology Scoring

Digital skin assessment isn't AI replacing the dermatologist, and it isn't a dermatologist eyeballing photos alone. The strongest approach scores the same standardized photographs two ways, with AI models and with dermatology grading.

Standardization comes first. If lighting, distance, or angle shifts between photos, a real change in the skin can't be told apart from a change in how the picture was taken. Haut.AI's platform, for example, runs capture through Live Image Quality Assurance technology that checks position, lighting, and framing before the image is taken, and it supports a clinical camera, a smartphone at a research site, or an at-home selfie (Personal Care Insights).

The AI layer brings scale and repeatability. Haut.AI reports intraclass correlation values of 0.97 to 0.98 for repeatability across five facial endpoints, holding across all three capture settings and across participants aged 20 to 70. The dermatology layer is the clinical anchor: Haut.AI says its grades correlate strongly with dermatology consensus ratings for structural aging signs and pigmentation. Together, the AI gives you consistency across thousands of images, and the dermatology scoring gives you an extra layer of clinical credibility.

That pairing is what makes skin a practical endpoint well outside the dermatology office. In Part 3, we'll show how it works inside an Alethios study: participants capture standardized photos from their phone, the images are scored by AI models and dermatology graders, and the results sit in the same study record as wearables, surveys, and at-home biomarker kits.

"We’ve had a great experience working with Alethios. Their platform has enabled us to incorporate innovative digital endpoints that objectively assess changes in skin health. Their team has also been incredibly helpful—connecting us with an expert to evaluate standardized photos alongside the digital measurements and helping us determine the best ways to assess both our skin and hair outcomes. It’s been a very collaborative process, and we’re excited to see what the final data show."

— Cassie Evans, Helaina

Bringing It Together

There is no single measure of “skin health,” and the amount of methods available to examine it are growing. Decentralized tools do not eliminate the need for onsite evaluation or clinical judgment, but they expand the range of questions researchers can study and make participation possible for people who may not live near a research site.

The strongest study design may combine methods. The right approach depends on the research question, participant population, required level of clinical oversight, budget, and intended use of the data.

Learn how you can evaluate skin health with Alethios Book a demo.