Basal transepidermal water loss: right/left forearm difference and motoric dominance

Background/alms: Evaporimetry and transepidermal water loss (TEWL) evaluations are among the most important means of approaching basic cutaneous physiology in terms of its epidermal barrier function. However, physiological skin complexity, together with the loose specifications currently available for analytical purposes, justify the need for further investigating and identifying eventual covariates and limiting factors with respect to both the epidermal barrier function issue and evaporimetry itself.

The relevant operating procedures were investigated with respect to the anatomical and functional equivalence of contralateral sites as they are often used in TEWL determinations and topically applied substance efficacy testing. The study was conducted on human volunteers using five different sites in both forearms, using a standard evaporimetry apparatus. Special attention was put on the right/left forearm difference regarding normal daily life motoric dominance reported by each individual.

A consistent difference between TEWL values measured at the most active arm was detected when compared with the readings from the opposite limb. Also, those sites placed nearer the extremities of the forearm behave differently from the inner ones.

All information thus gathered suggests that using contralateral sites in study protocols for TEWL determinations, particularly when one side is intended to act as control, requires awareness with respect to the physiological and functional differences of the sampling sites chosen. In any case, a proper randomisation and balancing of the experimental design is crucial.