Toward home-based skin hydration management of atopic dermatitis: A NIR hydration index for non-invasive monitoring

Xue, Yisong, Yao, Xiang, Chen, Zhaodong, Xu, Haihuan, Yang, Chenxi, Yang, Songqi, Yang, Chris ORCID: https://orcid.org/0000-0002-8429-7598 and Li, Ting 2026. Toward home-based skin hydration management of atopic dermatitis: A NIR hydration index for non-invasive monitoring. APL Photonics 11 (7) , 076106. 10.1063/5.0336955

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Abstract

Skin hydration serves as a key indicator for barrier integrity, especially in atopic dermatitis (AD), where its decline drives xerosis, itch, and disease progression. However, current hydration assessment methods are often limited by poor subsurface sensitivity, optical interference from surface lesions, and environmental noise, hindering portable real-time testing. Here, we present a compact dual-wavelength (910/970 nm) near-infrared diffuse-reflectance system designed for deep-skin hydration monitoring via a novel optical hydration index (OHI). By combining fixed-geometry acquisition with log-domain feature extraction, the system achieves enhanced sensitivity to subtle physiological changes. Furthermore, a temperature-aware regression algorithm was implemented to suppress instabilities caused by intensity fluctuations. Monte Carlo simulations were employed to optimize probe geometry and ensure sensitivity to subsurface photon paths within multi-layered skin models. The system’s performance was validated through ex vivo porcine skin dehydration experiments and benchmarked against commercial instruments in vivo. Our results demonstrate that the OHI effectively distinguishes AD patients from healthy individuals with high diagnostic accuracy and sensitively tracks short-term dynamic hydration changes following emollient application. This work provides a repeatable, objective framework for longitudinal skin management, paving the way for non-invasive, home-based AD monitoring.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Schools > Engineering
Publisher:	American Institute of Physics
ISSN:	2378-0967
Date of First Compliant Deposit:	13 July 2026
Date of Acceptance:	18 May 2026
Last Modified:	13 Jul 2026 09:58
URI:	https://orca.cardiff.ac.uk/id/eprint/188140

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