Plant that contains several components that can cause a negative reaction on skin when it is exposed to sunlight; however, this is a bigger concern when St. John's wort is taken orally. Like most plants, it's a rich source of antioxidants.
References for this information:
International Journal of Toxicology, Volume 20, 2001, Supplement pages 31-39
Hautarzt, April 1997, pages 249-52.
American Herbal Pharmacopoeia, 1997, pages 1-32