Final Report on the Safety Assessment of Lauramine Oxide and Stearamine Oxide

Abstract

Lauramine Oxide and Stearamine Oxide are aliphatic tertiary amine oxides that are used mostly in hair care products as foam builders and stabilizers, viscosity enhancers, emollients, conditioners, emulsifiers, antistatic agents, and wetting agents. Both compounds are susceptible to nitrosation and can form nitrosamines in the presence of nitrosating agents. In rats, up to 40% of Lauramine Oxide applied to the skin was absorbed. In two human volunteers, 92% of the dose applied to the skin was recovered from the skin. The oral LD50 in rats for a formulation containing 0.3% Lauramine Oxide was estimated to be >20 g/kg. At a concentration of 30%, Lauramine Oxide produced severe dermal reactions in rabbits, but at 0.3% only slight to moderate erythema with slight edema, Assuring, and slight to moderate epithelial desquamation were found. Stearamine Oxide applied to rabbit skin at 5% did not cause irritation. Both ingredients caused mild, transient ocular irritation in rabbits. Clinical data showed dermal exposure to 3.7% Lauramine Oxide to be a mild irritant, with a slight potential for mild cumulative skin irritation at concentrations as low as 2%. At 0.3%, Lauramine Oxide was not a sensitizer in clinical studies. Lauramine Oxide was nonmutagenic in the Ames assay, but was mutagenic after nitrosation. Lauramine Oxide at 0.1% in drinking water was not carcinogenic in rats, but at 0.1% with 0.2% sodium nitrate did increase the incidence of liver neoplasms. Based on this animal data, neither ingredient should contain N-ni-troso compounds nor be used in formulations containing nitrosating agents. On the basis of the available animal and clinical data, it is concluded that Lauramine Oxide and Stearamine Oxide are safe as cosmetic ingredients for rinse-off products, but that the concentration in Lauramine Oxide leave-on products should be limited to 3.7% and that of Stearamine Oxide limited to 5%.