05/27/2026
YOU NEED TO KNOW ABOUT WILD PARSNIP. Please share this widely.
Several years ago, when I was in graduate school, I had a patient come in with a terrible blistering rash. She had already been to several emergency departments over a period of weeks, and no one could tell her what it was.
The rash continued to blister, burn, and scar for weeks after it first appeared.
I was determined to figure it out. The pattern looked like it had to be from something outside — a plant, a bug, something in the environment. I contacted OSU Extension and asked if they knew of anything in Ohio that could cause severe, painful blisters that lasted for weeks.
They knew immediately.
Wild parsnip.
At the time, it was still relatively new to Ohio. Unfortunately, it is not rare anymore. According to OSU Extension, wild parsnip is now found throughout Ohio and can cause severe blistering when its sap gets on the skin and is then exposed to sunlight.
This reaction is called phytophotodermatitis — basically, the plant sap makes the skin dangerously sensitive to UV light. The rash may not show up right away; symptoms can start about 24 hours later and the blistering may peak 48–72 hours after exposure. That delay is one reason people often have no idea what caused it.
What to look for:
Wild parsnip can grow several feet tall and has yellow, umbrella-shaped flower clusters. It often grows along roadsides, trails, fields, ditches, and unmowed areas.
Please do not touch it. Do not weed-whack it. Do not mow through it without understanding the risk. The sap is the problem.
Take a minute to look at these photos from OSU Extension and learn how to recognize it: https://bygl.osu.edu/index.php/node/2614
This is one of those things most people have never heard of — until it happens to them.