PUVA treatment inhibits nonimmunologic immediate contact reactions to benzoic acid and methyl nicotinate

Final report on the safety assessment of benzaldehyde

Benzaldehyde is an aromatic aldehyde used in cosmetics as a denaturant, a flavoring agent, and as a fragrance. Currently used in only seven cosmetic products, its highest reported concentration of use was 0.5% in perfumes. Benzaldehyde is a generally regarded as safe (GRAS) food additive in the United States and is accepted as a flavoring substance in the European Union. Because Benzaldehyde rapidly metabolizes to Benzoic Acid in the skin, the available dermal irritation and sensitization data demonstrating no adverse reactions to Benzoic Acid were considered supportive of the safety of Benzaldehyde. Benzaldehyde is absorbed through skin and by the lungs, distributes to all well-perfused organs, but does not accumulate in any specific tissue type. After being metabolized to benzoic acid, conjugates are formed with glycine or glucuronic acid, and excreted in the urine. Little acute toxicity was seen. The oral LD(50) of Benzaldehyde in rats and mice ranged from 800 to 2850 mg/kg. The intraperitoneal LD(50) in white rats was 3265 mg/kg. In short-term oral studies, the no observed adverse effect level (NOAEL) was 400 mg/kg in rats and mice. In subchronic oral studies, the NOAEL was 400 mg/kg in rats and 600 mg/kg in mice. In a 16-week feeding study, rats given up to 10,000 ppm showed no signs of toxicity. Repeated inhalation of volatilized Benzaldehyde produced ocular and nasal irritation at 500 ppm and death in rabbits at 750 ppm. Undiluted Benzaldehyde was irritating to rabbit eyes, causing edema, erythema, and pain. Benzaldehyde was determined not to be a contact sensitizer, but did produce allergic reactions in a maximization test. Clinical reports of allergy to Benzaldehyde are rare. Benzoic Acid did not produce irritation or sensitization reactions in human clinical studies. Benzoic Acid also failed to produce reactions in phototoxicity and photosensitization tests. Neither Benzaldehyde, Benzoic Acid, nor Sodium Benzoate are reproductive or developmental toxicants at doses that are nontoxic to the mother. In a behavioral study, blood levels of 0.12 ng/ml Benzaldehyde produced a 44% reduction in motor activity in mice. Benzaldehyde did not produce mutations in bacterial assays, but did produce chromosomal abnormalities in Chinese hamster cells and increased mutations in a mouse lymphoma forward mutation assay. Benzaldehyde was evaluated by the National Toxicology Program, which found no evidence of carcinogenicity in rats, and some evidence of carcinogenicity in mice. Several studies have suggested that Benzaldehyde can have carcinostatic or antitumor properties. Overall, at the concentrations used in cosmetics, Benzaldehyde was not considered a carcinogenic risk to humans. Although there are limited irritation and sensitization data available for Benzaldehyde, the available dermal irritation and sensitization data and ultraviolet (UV) absorption and phototoxicity data demonstrating no adverse reactions to Benzoic Acid support the safety of Benzaldehyde as currently used in cosmetic products.

Final report on the safety assessment of Benzyl Alcohol, Benzoic Acid, and Sodium Benzoate

Benzyl Alcohol is an aromatic alcohol used in a wide variety of cosmetic formulations as a fragrance component, preservative, solvent, and viscosity-decreasing agent. Benzoic Acid is an aromatic acid used in a wide variety of cosmetics as a pH adjuster and preservative. Sodium Benzoate is the sodium salt of Benzoic Acid used as a preservative, also in a wide range of cosmetic product types. Benzyl Alcohol is metabolized to Benzoic Acid, which reacts with glycine and excreted as hippuric acid in the human body. Acceptable daily intakes were established by the World Health Organization at 5 mg/kg for Benzyl Alcohol, Benzoic Acid, and Sodium Benzoate. Benzoic Acid and Sodium Benzoate are generally recognized as safe in foods according to the U.S. Food and Drug Administration. No adverse effects of Benzyl Alcohol were seen in chronic exposure animal studies using rats and mice. Effects of Benzoic Acid and Sodium Benzoate in chronic exposure animal studies were limited to reduced feed intake and reduced growth. Some differences between control and Benzyl Alcohol-treated populations were noted in one reproductive toxicity study using mice, but these were limited to lower maternal body weights and decreased mean litter weights. Another study also noted that fetal weight was decreased compared to controls, but a third study showed no differences between control and Benzyl Alcohol-treated groups. Benzoic Acid was associated with an increased number of resorptions and malformations in hamsters, but there were no reproductive or developmental toxicty findings in studies using mice and rats exposed to Sodium Benzoate, and, likewise, Benzoic Acid was negative in two rat studies. Genotoxicity tests for these ingredients were mostly negative, but there were some assays that were positive. Carcinogenicity studies, however, were negative. Clinical data indicated that these ingredients can produce nonimmunologic contact urticaria and nonimmunologic immediate contact reactions, characterized by the appearance of wheals, erythema, and pruritus. In one study, 5% Benzyl Alcohol elicited a reaction, and in another study, 2% Benzoic Acid did likewise. Benzyl Alcohol, however, was not a sensitizer at 10%, nor was Benzoic Acid a sensitizer at 2%. Recognizing that the nonimmunologic reactions are strictly cutaneous, likely involving a cholinergic mechanism, it was concluded that these ingredients could be used safely at concentrations up to 5%, but that manufacturers should consider the nonimmunologic phenomena when using these ingredients in cosmetic formulations designed for infants and children. Additionally, Benzyl Alcohol was considered safe up to 10% for use in hair dyes. The limited body exposure, the duration of use, and the frequency of use were considered in concluding that the nonimmunologic reactions would not be a concern. Because of the wide variety of product types in which these ingredients may be used, it is likely that inhalation may be a route of exposure. The available safety tests are not considered sufficient to support the safety of these ingredients in formulations where inhalation is a route of exposure. Inhalation toxicity data are needed to complete the safety assessment of these ingredients where inhalation can occur.

Evaluation of skin blood flow by laser Doppler flowmetry

Laser Doppler flowmetry is an excellent noninvasive technique for the measurement of cutaneous microcirculation. The list of applications of laser Doppler flowmetry in dermatology is long. It can be applied to monitor inflammation caused by various drugs, chemicals, and allergens related to blood flow. To measure certain inflammatory reactions a combination of other bioengineering measurements is desirable. Flaps can be monitored, and burn depth measured by laser Doppler flowmetry. Through blood flow measurement, the pathophysiology of various skin diseases can be verified and certain treatments can be partially monitored. Although it is not as directly applicable to daily clinical practice, except in a few cases, laser Doppler flowmetry is a very useful technique in various kinds of dermatologic research.