Transepidermal water loss (TEWL)

Method

Water flux through the epidermis by open- or closed-chamber evaporimetry (tewametry) at a defined anatomical site, under controlled room temperature and humidity after a stated acclimatisation period. Site, device and acclimatisation conditions are recorded on the edge, and sites are reported separately.

The method is part of the endpoint identity. Studies measuring the same quantity by a different method are held as separate endpoints.

Notes

SIGN INVERSION HAZARD against CAT:outcome/stratum-corneum-hydration measured by corneometry: both are labelled skin barrier function, both are taken at the same visit on the same site by devices from the same manufacturer family, and their polarity is OPPOSITE - this improves by FALLING and corneometry hydration improves by RISING. They also measure different things, barrier integrity versus surface water content. Strongly site-specific, and the sites dissociate - in PMID 34214362 ceramide improved this at one site and not another - so a site-blind pooled edge is not comparable to a site-specific one.