Sensitizing and irritating properties of star anise oil.

Star anise oil in 2 and 1% concentrations produced active sensitization in 5% of test subjects, and positive patch tests in 36 and 34%, respectively, of consecutive patients with dermatitis. A comparison of the results of tests with balsams and other essential oils showed that star anise oil does not give cross-reactions and pseudo cross-sensitivity. Patients positive to this oil are frequently positive to anethole and to other constituents of this oil: alpha-pinene, limonene and safrole. In tests with star anise oil it is noteworthy that a 1% concentration is strongly irritant, and 0.5% reveals sensitivity in only one fifth of the actively sensitized subjects. It is possible that the cause of false negative patch tests might be similar in the case of some other allergens.