Absorption of triphenylmethane dyes Brilliant Blue and Patent Blue through intact skin, shaven skin and lingual mucosa from daily life products

Currently, there is evidence of health risks of triphenylmethane dyes after systemic absorption. This paper investigates the fate of Brilliant Blue (BB) and Patent Blue (PB) after 24-h in vitro diffusion, firstly through intact and secondly through shaven pig-ear skin (stored by freezing) from four leave-on cosmetics under in-use conditions. Both dyes showed no measurable permeation through intact skin but significant permeation was found through shaven skin. From 250 ng/cm2 of dye in one applied dose there were found 52 ng/cm2 of BB and 91 ng/cm2 of PB from ethanol-based after-shave, 39 ng/cm2 of BB and 86 ng/cm2 of PB from ethanol-free facial-cleanser, 35 ng/cm2 of BB and 43 ng/cm2 of PB from O/W emulsion, and no amount from W/O emulsion, as available to become systemically absorbed. Thirdly, the paper focuses on lingual mucosa after licking lollipops. Ex vivo porcine tongue dorsum was exposed to human saliva with 15,000 ng/cm2 of dye for 20 min. 24-h diffusion resulted in 34 ng/cm2 of BB and 86 ng/cm2 of PB which can be directly absorbed into the blood system. Findings are troubling, particularly with regard to the frequent use of after-shave products by the male population and repeated lollipops licking by children.

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► Shaving significantly increases skin permeation of triphenylmethane dyes mainly from ethanol-based after-shave.
► Tongue is permeable for Brilliant Blue FCF and Patent Blue V from human saliva.
► The risk of systemic absorption of synthetic dyes should be explored also via slightly damaged skin and lingual mucosa.