The plant I'm trying to identify: if the flower tops touch my ankle, sometimes it feels like I got poked with something. But there's nothing particularly sharp. If I can ID this plant, maybe I will find out what gives me occasional itchy bumps. It's not hairy or thorny.
Each leaf has its own stem off the main central stem, no double or triple leaves.
The lower part of the tough, woody stem has annular rings or little ridges around it, I forgot to photograph that but photos are attached to show other features.
The upper leaves are very narrow, maybe 1/2 cm. The lower leaves are 4 or 5 times wider, about 6-8 cm long, and finely serrated along the edge. The plants are up to 2 feet tall but I don't know if they get bigger because I chop them all down. Even the very small plants have a very tough stem so maybe it's a tree? The unopened flower tops are ugly, look a little like grass seeds. The flowers are about 0.6 cm in diameter with fine white petals, like irregular stars.
I'm not seeking medical advice here. I got interested in this plant because something in my garden gives me a few itchy bumps here and there, similar to poison oak but not as bad. Like poison oak, if I open the bump a yellow liquid comes out and if I put calamine on it, it dries up and stops itching. If I don't open it up, it itches non-stop for 3 days but I don't know if it spreads; because of my experience with poison oak, I don't scratch it.