What TEWL measures.
TEWL describes water vapor leaving through the stratum corneum. Higher values are generally associated with a more disrupted barrier, while lower values are generally associated with healthier barrier function.
The measurement depends on the instrument, environment, acclimation period, body site, and study protocol. A result should therefore be read with its method and conditions.
The published numbers need context.
A systematic review and meta-analysis identified TEWL estimates for 86 skin areas across 212 studies. In that review, pooled estimates ranged from 2.3 g/m²/h on breast skin to 44.0 g/m²/h in the axilla.
That wide range is a reminder that anatomy matters. A value from one location should not be treated as a universal normal range for every part of the body.
What a serum claim would still need to show.
To connect a topical product with a barrier outcome, look for a controlled human study of the finished formula, a defined application schedule, a named measurement method, and results that include uncertainty and a comparison group. An ingredient theory alone cannot supply those details.
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Selected authoritative sources
These sources are provided so you can inspect the study type, molecule, route, and limitations directly. They do not endorse a VitaPep product.