Skin irritancy of commercially available alkyl ether sulphate surfactants: is there a difference between those with alkyl chains consisting of even or odd numbers of carbon atoms?

Various concentrations of commercially available alkyl ether sulphate surfactants with alkyl chains consisting of even or odd numbers of carbon atoms have been tested for their primary irritancy to rabbit skin in vivo. All six surfactants (2 with even and 4 with odd carbon number) produced skin irritation. The level of irritation showed dose-dependent increases in the concentration range 4-12% (w/w), with a plateauing of responses of moderate to severe irritation occurring between 12 and 24% (w/w). Recovery generally took 10-14 days to occur. There were no significant differences in the intensity or duration of response between surfactants with alkyl chains consisting of even and odd numbers of carbon atoms.