Hydration vs. skin permeability to nicotinates in man

Area of Science:

• Dermatology
• Biophysics
• Pharmacology

Background:

• Prolonged skin occlusion elevates stratum corneum water content, potentially increasing permeability and irritant dermatitis.
• Diaper wetness is a significant factor in diaper dermatitis onset.
• Optimizing diapering may reduce skin hyperhydration and dermatitis.

Purpose of the Study:

• Quantify the relationship between nicotinate ester skin permeability and hydration.
• Measure hydration using water evaporation rate (WER), decay curves, and WER-area under the curve (WER-AUC).
• Determine skin hydration and nicotinate permeability after a diapering simulation.

Main Methods:

• Nine healthy adult women participated in the study.
• Subjects underwent wet occlusive patch (10 min, 30 min, 3h) and wet model diaper (3h, 8h) exposures on forearms.
• Basal measurements of WER, blood flow volume (BFV), capacitance (Cap), and redness (a*) were taken before occlusions.
• Nicotinate esters (methyl and hexyl) were applied post-occlusion, with subsequent measurements of WER, Cap, a*, and BFV.

Main Results:

• Skin hyperhydration, indicated by WER-AUC, increased with exposure time for both patches and diapers.
• All occluded sites showed significantly increased hydration compared to controls.
• Nicotinate redness increased on hydrated skin but did not correlate with the degree of hyperhydration.
• Capacitance increased with patch occlusion but not diaper occlusion.

Conclusions:

• Wet patches and diapers increase skin hyperhydration proportionally to exposure time.
• Nicotinate permeation increased on hydrated skin, even after short exposure (10 min).
• No increased permeation was observed with further hyperhydration beyond a low threshold.
• WER-AUC is superior to capacitance for measuring hyperhydration; the model is suitable for evaluating diaper performance and occlusive therapy.