Hair removal and bioavailability of chemicals: Effect of physicochemical properties of drugs and surfactants on skin permeation ex vivo.

Cosmetic hair removal procedures are everyday routines in our society. However, it is unclear if such routines lead to increased uptake of applied substances such as drugs or formulation compounds, potentially resulting in skin irritation or sensitization. The aim of this study was to elucidate the effect of common depilation and epilation methods on skin penetration of two surfactants and four model drugs of different physicochemical properties using the porcine ear model. It should be elucidated whether the substances' skin penetration behavior would be affected by hair removal procedures and if potential effects would be related to their polarity. Confocal Raman spectroscopy revealed no effect of hair removal on total penetration depths of SDS and sulfathiazole. Significantly higher relative penetrated amounts within 0-6 µm of stratum corneum depth were found for SDS after dry shaving, depilatory cream and waxing and for sulfathiazole after all depilation methods and partly after epilation. ATR-FTIR spectroscopy revealed no effect of hair removal on the penetration depth of lecithin LPC80, but higher relative amounts at the skin surface after wet shaving and electric epilation. Diffusion cell experiments using a lecithin-based microemulsion as carrier system for fluconazole, fludrocortisone acetate and flufenamic acid showed higher cumulative amounts, higher drug fluxes and shorter lag times for the more lipophilic drugs for some of the methods, but only shorter lag times in some cases for fluconazole. In summary, the observed effects appeared to depend on drug polarity and experimental setup.

Effect of Physical and Chemical Hair Removal Methods on Skin Barrier Function in vitro: Consequences for a Hydrophilic Model Permeant.

BACKGROUND: Although very common in our society, the effect of hair removal on physiological skin parameters and on the ingress of applied chemicals has not been systematically investigated. Thus, as a first step, the aim of the present study was to elucidate the effect of hair removal through epilation (electric epilation, waxing) and depilation (dry and wet shaving, depilatory cream) on skin properties in vitro using the porcine ear model. METHODS: Attenuated total reflection Fourier transform infrared spectroscopy, measurement of the transepidermal water loss (TEWL), visualization by capacitance-based contact imaging, confocal Raman spectroscopy (CRS), diffusion cell studies and tape stripping experiments were employed. RESULTS: Increased TEWL and altered skin permittivity maps were observed. Decreased stratum corneum thickness was observed after waxing. Diffusion cell studies showed increased skin permeation especially in case of dry shaving, electric epilation and waxing. CONCLUSION: Considering CRS and diffusion cell data, a moderate if significant decrease in skin barrier function was found after hair removal by dry shaving (physical skin/material interaction) and epilation methods (plucking out the entire hair, for example, by electrical epilation and waxing). Subsequent experiments will include testing of different permeants covering a broad range of physicochemical properties in vitro and confirming our findings in vivo.

Penetration monitoring of drugs and additives by ATR-FTIR spectroscopy/tape stripping and confocal Raman spectroscopy - A comparative study.

Vibrational spectroscopy is a useful tool for analysis of skin properties and to confirm the penetration of drugs and other formulation compounds into the skin. In particular, attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy and confocal Raman spectroscopy (CRS) have been optimised for skin analysis. Despite an impressive amount of data on these techniques, a comparative methodological assessment for skin penetration monitoring of model substances is still amiss. Thus, in vitro skin penetration studies were conducted in parallel using the same porcine material and four model substances, namely sodium laureth sulfate (SLES), sodium dodecyl sulfate (SDS), sulfathiazole sodium (STZ) and dimethyl sulfoxide (DMSO). ATR-FTIR spectroscopy in combination with tape stripping and CRS were employed to evaluate the skin penetration of the applied substances. In addition, the skin hydration status or change in skin hydration after application was investigated. The results show that both methods provide valuable information on the skin penetration potential of applied substances. The penetration profiles determined by CRS or ATR-FTIR/tape stripping were comparable for all substances; a slow decrease in relative substance concentration was visible from the skin surface inwards within the stratum corneum (SC). In general, deeper penetration into the SC was observed with CRS, which may be related to the depth resolution of the employed device. However, when related to the respective total SC thickness of each experiment, the penetration depths determined by parallel CRS and ATR-FTIR analysis were in good agreement for all model substances. The observed order of the penetration depth was DMSO > SDS > SLES > STZ with both techniques. A decrease of the relative concentration to 10% of the maximum value was found approximately between 34 and 89% of total SC thickness. Summarising these findings, advantages and drawbacks of the two techniques for in vitro skin penetration studies are discussed.