Allergic contact dermatitis from 12-hydroxystearic Acid and hydrogenated castor oil.

A 34-year-old male experienced severe allergic contact dermatitis from 12-hydroxystearic acid in a lip balm and from hydrogenated castor oil in an underarm deodorant. He also had a positive patch-test reaction to bis-diglyceryl polyacyladipate-2, which is present in the implicated lip balm and which itself contains 12-hydroxystearic acid. He was also incidentally found to have contact allergy to ricinoleic acid and castor oil. Ricinoleic acid is the principal fatty acid in castor oil, whereas 12-hydroxystearic acid is the principal fatty acid in hydrogenated castor oil. These two fatty acids are each 18-carbon 12-hydroxylated fatty acids, differing only in degree of saturation. The lack of patch-test reactivity to the analogous nonhydroxylated fatty acids, stearic acid (C18:0), and oleic acid (C18:1) indicates that 12-hydroxylation was required for allergenicity in this patient. In addition, serial dilution testing demonstrated that saturation of the hydroxylated C18 fatty acid enhanced its allergenicity.