Quinophthalone is a dye with distinctive greenish yellow color. Quinophthalone is used as coloring agents for various materials. Quinophthalone is a strong sensitizer in guinea pigs, and its threshold concentration for induction and challenge is 10 ppm.
References:
[1]. Gi Rim Han, et al. Shedding new light on an old molecule: quinophthalone displays uncommon N-to-O excited state intramolecular proton transfer (ESIPT) between photobases. Sci Rep. 2017 Jun 20;7(1):3863.
[2]. Y Sato, et al. D&C nos. 10 and 11: chemical composition analysis and delayed contact persensitivity testing in the guinea pig. Contact Dermatitis. 1984 Jan;10(1):30-8.