Transonychial water loss in healthy and diseased nails

The objective of this study was to determine the transonychial water loss (TOWL) in both healthy and affected nails in different diseases and to compare it with the transepidermal water loss (TEWL). TOWL was measured by a new evaporimetric method: Plasticine was used to fix the protection cover of the evaporimeter probe to the nails. The TOWL behaved contrary to the TEWL. Affected nails in patients with atopic eczema (p <0.01), psoriasis (p<0.05) and onychomycosis (p<0.001) showed a significantly lower TOWL than did nails of healthy test subjects. The decrease in TOWL in diseased nails in comparison to healthy nails could be due to the formation of a stratum granulosum in atopic, psoriatic or fungus-affected nails, as this layer is normally absent in healthy nails.