Pennsylvania Department of Agriculture field technician Jason Fuller shows a small young giant hogweed plant before spraying to kill it. Hogweed can be dangerous to people. Its sap causes a change in human skin that causes blisters when exposed to sunlight and even blindness.

Giant hogweed is making the news.

According to the South Carolina and North Carolina Exotic Plant Pests Council, the plant "with toxic sap that can cause severe burns" has been located in North Carolina, but not in South Carolina. Let’s all breathe a sigh of relief.

Plants, giant hogweed included, protect themselves in many ways. Sometimes it’s thorns, but often they produce chemicals that repel or cannot be digested by insects or other herbivores. 

Giant hogweed has a unique way of warding off offenders by producing chemicals that cause skin to become extremely sensitive to light. According to the U.S. Department of Agriculture, this "noxious weed" can cause skin irritation and even blindness. 

Likewise, poison ivy affects skin cells.

Many of you know exactly what I’m talking about.

Homes Poison Ivy

Ninety percent of people are allergic to poison ivy. The sap contains urushiol oil in the leaves, roots, stems and berries and is active even if the plant is dead.

“Leaves of three, let it be” never really helped me identify poison ivy. There are many plants with three leaves. It is a vine, that’s helpful, but the foliage has slight variations. There are three leaflets, that is true, but sometimes they’re slightly lobed and sometimes not. The petioles are often red, but not always. The vine can be quite woody, depending on how old it is, and nearly always hairy with tendrils that allow it to grip a tree or wall or just grow along the ground like the world’s worst groundcover.

Odds are good that you’re allergic to poison ivy. If you’re one of the few who aren’t, don’t press your luck. Just stay away and be thankful. You can always develop an allergy. There are plenty of stories of someone showing off and it goes horribly wrong.

Poison Ivy with lobed leaf mar

Poison ivy's characteristic three leaflets can feature various margins, in this cased, lobed ones.

What happens to most of us when we touch poison ivy is a reaction to the sap. The entire plant contains an active ingredient called urushiol that will react with your skin in winter or summer, whether the plant is dead or alive. And if it’s burned, urushiol can be inhaled and could be fatal.

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Skin responds to urushiol by forming blisters. Direct contact or primary exposure will cause the worst symptoms, but secondary exposure, such as touching tools or clothing that have sap on it, can cause mild reactions. I kept picking up a rash earlier this year and realized our dogs were walking through it on one particular path. The dogs were fine, but I was getting secondary exposure.

Symptoms can occur within a day after primary exposure. Secondary exposures might show up a few days later. If you wash the area with soap and water within 30 minutes or so after exposure, depending on your sensitivity, you can remove the urushiol before it binds to the skin. There are preventive products, such as Tecnu and Ivy Block, that can be applied before exposure to prevent a rash, and even some products that scrub the urushiol off. Diligence and soap, though, is still effective.

A few years ago, a tree fell in our backyard and it was tangled with poison ivy. I spent half an hour working on it each time before coming in to shower, careful to wash any clothing I was using or tools that were exposed. It took weeks to finish the job, but I never got a rash.

The problem, however, is we often don’t realize when we’ve been exposed. Once that happens, all you can do is manage the itch until it goes away. In my experience, it takes two weeks. For others, it might be a little longer. Days seven through 10 are the worst.

There are over-the-counter products and prescription lotions that relieve the symptoms, but they work differently for everyone. Often times, hot water is the only thing that works for me. I’ve taken showers in the middle of the night just to get relief for a couple of hours.

If you can’t take the itch, or the rash is near your eyes or in another very sensitive area, go to the doctor for a steroid shot or Prednisone, a corticosteroid that helps the body fight illnesses and injuries.

The results vary, but I’ve had to expedite some serious cases and was glad I did so.

Tony Bertauski is a horticulture instructor at Trident Technical College. To give feedback, e-mail him at