California Code, Health and Safety Code - HSC § 108175

“Strong sensitizer” means a substance that will cause on normal living tissue through an allergic or photodynamic process a hypersensitivity that becomes evident on reapplication of the same substance and that is designated by the department. Before designating any substance as a strong sensitizer, the department, upon consideration of the frequency of occurrence and severity of the reaction, shall find that the substance has a significant potential for causing hypersensitivity.