Wild parsnip is an eye-catching weed that hails originally from Europe and Asia. Wild parsnip grows in large patches or as scattered plants along roadsides, in abandoned fields, on pastures, on restored prairies, and in disturbed open areas. According to this article, wild parsnip can cause chemical-type burns on exposed human skin. News to me. I've spent probably fifty or more hours shooting insects on this plant, and I have never experienced any adverse reactions.

"There are chemicals in wild parsnip called psoralens (precisely, furocoumarins) that cause what dermatologists call "phyto-photo-dermatitis." That means an inflammation (itis) of the skin (derm) induced by a plant (phyto) with the help of sunlight (photo). When absorbed by skin, furocoumarins are energized by ultraviolet light (present during sunny and cloudy days) causing them to bind with nuclear DNA and cell membranes. This process destroys cells and skin tissue, though the reaction takes time to produce visible damage."
- From "Burned by Wild Parsnip" - Wisconsin Natural Resources Magazine