6 Itchy-Rash Plants and How to Identify Them

Stinging nettles cannot swoop in on you and deliver a burning sting, as yellow jackets can. But if you accidentally run through a patch of these plants with bare legs, it will feel a bit like a swarm of tiny yellow jackets just attacked your appendages. 

Poison ivy has three leaves (as does poison oak), which makes it easier to spot. Brushing poison ivy will make your skin come into contact with urushiol, the oil that causes an itchy, blistering rash.

Poison sumac's leaf is shaped like a feather, which distinguishes it from poison ivy. But it has the same oil, urushiol, which can last from 12 to 72 hours depending on your condition.

It is widely recognized now that the ragweeds (both the giant variety and common ragweed) are the worst culprits behind hay fever in the autumn. What is not so widely known is that the ragweeds can also cause skin rashes if you touch them. Once you learn what ragweed looks like, remove it from your property (while wearing gloves, a long-sleeved shirt, etc.) so that you do not accidentally brush up against it while performing yard maintenance.

The story of the arrival of giant hogweed (Heracleum mantegazzianum) to North America is a common one. Like Japanese knotweed (Polygonum cuspidatum), for example, it was discovered growing in its native Asia by Western plant explorers, who found it highly ornamental. They brought it back with them, first to the U.K., then to the U.S. Only after it had escaped into the wild in its new homelands did people start to realize what a potent enemy they had let in. In fact, the potency of giant hogweed is indicated in its genus name, Heracleum, a nod to Heracles, the famously powerful hero of Greek mythology. This weed may, in fact, be the worst of the itchy-rash plants. It can cause not only rashes but even blindness.

Even some highly-valued plants like Christmas poinsettias can cause rashes and make you itch (or worse). It is a myth that if you eat a poinsettia leaf you will die, but do not let your guard down about poinsettias. It so often happens that in the process of busting of one myth, it spawns another. The new myth surrounding poinsettias is that they are totally harmless for everyone. That is simply false.