I was called by a homeowner in Gresham last week. His brother was weeding in the yard and shortly after his skin and eyes felt like they were on fire. It turned out that the plant was myrtle spurge (Euphorbia myrsinites), also known as donkey-tail spurge. This plant is listed as a noxious weed by the Oregon Department of Agriculture, and cannot legally be grown or sold in Oregon.
Some people, like the person who contacted us, have it in their yard and have no idea what it is. Others get the plant from friends and neighbors. The first take home message is that all Euphorbia's have a latex sap that can cause skin burns and eye damage. Some people are more sensitive than others. From reading on the web about the bad experiences people have had with this plant, it seems necessary to wear goggles, gloves, long pants, long-sleeved shirt, and shoes (not sandles) when dealing with Euphorbias, just in case. It is also important to wash immediately after handling these plants.
The second take home message is beware the free plant. Most plants that people have to share are somewhat invasive in the garden; that is why they have some to spare. And while not all free plants are toxic, be careful just in case because you might get burned.