Effect of layered application on the skin permeation of a cosmetic active component, rhododendrol

Abstract

Cosmetics containing rhododendrol (RD) were voluntarily recalled after incidents of leukoderma related to their use. Users reported using up to five different RD-containing products by layered application. In this study, we investigated the effects of layered application, formulations, and their components on the skin permeation of cosmetics containing RD. Experiments were designed to simulate actual in-use conditions, such as varying application volumes, physical mixing of formulations, sequence of cosmetics application and time interval between applications, to establish their effect on the skin permeation of RD. Milk and lotion RD-containing cosmetics (2%), 1% aqueous RD, and preparations of formulation components were applied as the first or second layers as finite doses of 10 or 20 µL/cm 2 . Permeation experiments were performed through excised porcine ear skin using Franz diffusion cells with an effective diffusion area of 1.77 cm 2 . Cosmetics applied by layered application exhibited lower skin permeation of RD compared with a single application despite having the same application dose. High initial volume (20 µL at 0 or 5 sec) did not exhibit any significant reduction in the permeation of RD. Formulations and their components caused varying reductions in RD permeation, probably due to changes in thermodynamic activity of the active component. Layered application, formulation components, application volume, time interval and sequence of application had significant influences on the skin permeation of the active component. Moreover, this study established a method of investigating the influence of formulations and their components on the skin permeation of actives after layered application.

Halal Cosmetics: A Review on Ingredients, Production, and Testing Methods

“…Detection and quantification of cosmetic actives in skin (SC and VED) following dermal absorption has long been established [96][97][98][99][100]108,114,115]. Quantification of cosmetic actives permeating through the skin following actual in-use conditions, such as layered application, has been reported recently [116]. Together, these methods could provide insights into product formulation development with respect to the permeation of ingredients.…”

Usefulness of Artificial Membrane, Strat-M®, in the Assessment of Drug Permeation from Complex Vehicles in Finite Dose Conditions

“…Porcine skin was isolated from frozen edible porcine ears kept at −80 • C. The preparation and isolation of full-thickness porcine ear skin was performed in accordance with our previous report [11]. To ensure uniformity, skin from the central dorsal region of the ears was harvested.…”

“…Figure 1 illustrates the cumulative amount of RD that permeated through porcine skin and Strat-M ® . RD formulations were applied in finite doses (single application of 10 µL/cm 2 , layered application of 10 µL/cm 2 and 10 µL/cm 2 , and single application of 20 µL/cm 2 ) to simulate in-use conditions, such as layered application and dose in human exposures to the liquids [10,11]. Permeation of RD from aqueous and complex vehicle-based formulations through porcine skin showed a dose-dependent rank order except for the layered application, where permeation was lower compared with a single application of 20 µL/cm 2 , despite having the same total applied dose.…”

“…The Scientific Committee in Consumer Safety (SCCS) stipulates the conditions for in vitro dermal absorption studies of cosmetics, where experimental dose or the amount applied during use (i.e., layered application), formulation (e.g., finished cosmetics products, complex vehicles), and barrier integrity must be met. Furthermore, sample application during in vitro experiments should mimic human exposure normally at 10 µL/cm 2 for liquid formulations [9][10][11][12]. In this study, the design of permeation experiments encompassed finite and infinite dose conditions, layered application, the effect of solvents/complex vehicles, and residual formulations to establish the usefulness of the artificial membrane in assessing the permeation of rhododendrol, a lipophilic molecule, and caffeine, a hydrophilic molecule, as model drugs in simulated in-use conditions.…”

Physical Properties of an Ionic Liquid Composed of Two Water-Soluble Vitamins and Enhanced Skin Permeation of Both Vitamins

“…Then, full-thickness abdominal skin was excised from the body. The subcutaneous fat and blood vessels were carefully removed on the dermis side from the excised skin, and the skin was mounted on a vertical diffusion cell (cell volume: 6.0 mL, effective permeation area: 1.77 cm 2 ) [25]. To prevent oxidative degradation of VC and to hydrate the skin, 1.0 and 6.0 mL of phosphate buffered saline (PBS) containing 0.3% homocysteine were applied to the stratum corneum and dermis side, respectively, for 1 h before the skin permeation experiment.…”