Anthracene
Anthracene, a compound found in the herb uva ursi. Large amounts can cause skin damage as well as burning and itching associated with irritation of the conjunctiva and upper airways. The toxic effects of anthracene are similar to those of coal tars distillation products, and depend on the proportion of heavy fraction contained in it.
References
Leung, Albert Y. 1980. Encyclopedia of Common Natural Ingredient used in Food, Drugs and Cosmetics. John Wiley and Sons, N Y. 409 pp.
Toxnet, N.L.M. Toxicology Data Network. National Library of Medicine. Bethesda, Maryland.
Windholz, Martha, Susan Budavani, et. al. 1976. The Merck Index. Merck and Co., Inc. New Jersey.