The fate of dermally applied [14C]d-limonene in rats and humans.

The fate of dermally applied [(14)C]d-limonene was evaluated in humans and Long-Evans rats. In rats, 5 mg/kg body weight of [(14)C]d-limonene applied dermally to the shaved back under occlusion, resulted in the absorption of approximately 12% of the dose. The absorbed d-limonene was completely metabolized and excreted rapidly, primarily from the urine (80%) with a small fraction (20%) excreted in the feces. There was no long-term retention of the test material in body tissues. In humans, following dermal application of 12 mg of [(14)C]d-limonene in ethanol (1 mL) to the back under nonocclusive conditions (for 1 h after application to allow the material to dry, thereafter under occlusion), only 0.16% of the dose was absorbed and the radioactivity was recovered from the urine. Radioactivity in human feces was below the limit of detection. These results indicate that under conditions of simulated use of fragrances and cosmetics, d-limonene has a low potential for dermal absorption and tissue accumulation, and the d-limonene that is absorbed is rapidly excreted in the urine. Based upon these findings and the knowledge that d-limonene possesses a low-systemic toxicity profile, it is reasonable to conclude that dermal exposure to d-limonene from fragrance and cosmetic applications is highly unlikely to result in any clinically significant human toxicity.

The pharmacokinetics of phenylethyl alcohol (PEA): safety evaluation comparisons in rats, rabbits, and humans.

The present studies were conducted to compare the dermal absorption, plasma pharmacokinetics, and excretion of phenylethyl alcohol (PEA) by pregnant and nonpregnant rats, rabbits, and humans. The PEA is a natural fragrance material that is widely used in perfumes, soaps, and lotions and is a major ingredient of natural rose oil. Following dermal (430, 700, or 1400 mg/kg body weight [bw]), gavage (430 mg/kg bw), or dietary (430 mg/kg bw) administration of PEA to rats, plasma concentrations of PEA were found to be low regardless of the route of administration. The plasma concentrations of phenylacetic acid (PAA, the major metabolite of PEA) greatly exceeded the concentrations of PEA and were highest after gavage, followed by dermal then dietary administration. Absorption, distribution, metabolism, and excretion were compared following topical application of ¹4C-labeled PEA to rats, rabbits, and humans (specific activities of dosing solutions: 58-580, 164, and 50 µCi/mL, respectively). In rabbits, the plasma concentration-time profile for PAA was markedly prolonged compared to rats or humans. In humans, only 7.6% of the applied dose of PEA was absorbed, versus 77% in rats and 50% in rabbits. Based on a human dermal systemic exposure of 0.3 mg/kg per day from the use of multiple consumer personal care products containing PEA, a rat dermal no observed adverse effect level of 70 mg/kg per day, and the percentage of dose absorbed in humans, the margin of safety exceeds 2600 concluding that, under normal fragrance use conditions, PEA is not a developmental toxicity hazard for humans.

Dermal absorption and disposition of musk ambrette, musk ketone and musk xylene in human subjects.

Musk ambrette, musk ketone and musk xylene have a long history of use as fragrance ingredients, although musk ambrette is no longer used in fragrances. As part of the review of the safety of these uses, it is important to consider the systemic exposure that results from these uses. Since the primary route of exposure to fragrances is on the skin, dermal doses of carbon-14 labelled musk ambrette, musk ketone and musk xylene were applied to the backs (100 cm2) of healthy human volunteers (two to three subjects) at a nominal dose level of 10-20 microg/cm2 and excess material removed at 6 h. Means of 2.0% musk ambrette, 0.5% musk ketone and 0.3% musk xylene were absorbed based on the amounts excreted in urine and faeces during 5 days. Most of the material was excreted in the urine with less than 10% of the amount excreted being found in faeces. No radioactivity was detected in any plasma sample, consistent with low absorption, and no radioactivity was detected (<0.02% dose) in skin strips taken at 120 h. Analysis of urine samples indicated that all three compounds were excreted mainly as single glucuronide conjugates. The aglycones were chromatographically different, but of similar polarity, to the major rat metabolites excreted in bile also as glucuronides.