Poison ivy. Credit: Wikimedia Commons

Capable of causing an itchy rash and sores that can last for weeks, poison ivy is one of the few plants in the Maine wilderness that people need to watch out for — and it’s extremely common.

As the weather warms and people start spending more time outdoors gardening, hiking, hunting and more, now is a good time to refresh your knowledge about this troublesome plant. What does it look like? What should you do if you mistakenly touch it? Here are the answers to those important questions and more.

1. “Leaves of three, leave it be.”

This common saying is often used to describe poison ivy, but what does it really mean? Poison ivy is a woody perennial that produces groups of three leaflets, with the middle leaflet often larger than the other two. Aside from that defining characteristic, poison ivy plants differ greatly in appearance. The leaves can be glossy or dull. The edges of the leaves can be toothed, smooth or lobed. And the actual plant can be in the shape of an upright shrub or woody vine. That’s why, while there are other plants that have “leaves of three,” the safest thing you can do is not touch any plants with groups of three leaflets.

Poison ivy leaves turn reddish in the fall. And in the spring, the plant produces clusters of small yellow-green flowers, which are replaced by green berries that turn light gray or white later in the season. Native to New England, the plant can be found in many different habitats, including woodland edges, gardens, roadsides and riverbanks. It grows in areas that get partial shade to full sun, and it has adapted to thrive in a wide range of soil moisture conditions, according to the UMass Extension Landscape, Nursery and Urban Forestry Program.

2. It’s all about an oily liquid called urushiol.

Poison ivy produces an oily liquid called urushiol, which causes most people to have an allergic reaction in the form of a terrible rash. This liquid coats the entire plant — the leaves, stems, roots, berries. Everything.

About 85 percent of people develop an allergic reaction when they come into contact with urushiol, according to the American Academy of Dermatology. The rest of people don’t react at all — but that may not always be the case. People can develop sensitivity to urushiol over time, perhaps due to repeated exposure to it. Conversely, some people become less allergic to the oil over time.

3. The rash can vary in severity and timing.

The allergic reaction caused by urushiol varies depending on the person. Common symptoms are intense itching, rash, swelling, blisters, clear or yellow drainage and red, leathery skin. Severe reactions can include difficulty breathing and swallowing, swelling on your face or eyes and fever.

The rash usually develops 12 to 48 hours after exposure, according to the Mayo Clinic, and lasts for two to three weeks. However, everyone’s reaction varies somewhat. The severity of the rash and how quickly it develops can depend on several factors, including how sensitive the person is to urishinol and the amount of urishinol the person comes in contact with.

People who are especially sensitive to the oil can develop a rash in just a few hours. While people who are less sensitive to the substance can take up to 10 days to develop a rash. Also, areas of the body with thinner skin can develop the rash more quickly than areas of the body with thicker skin. And if it’s your first time getting a poison ivy rash, the symptoms may last as long as three to four weeks, according to the American Osteopathic College of Dermatology, while subsequent poison ivy rashes will likely not last as long.

4. It’s easy to spread the rash — sort of.

Because a poison ivy rash can develop in different areas of the body at different times, people may think they are spreading the rash by touching it. That’s not the case. The rash itself is not spreadable or contagious. Only urushiol can spread the rash.

After contact with the plant, people often mistakenly move the urushiol around their body with their fingers. This causes the rash to form in multiple places. It’s often how a person gets a poison ivy rash on their face. This is difficult to avoid if you don’t know that you have come into contact with a poison ivy plant. One preventative measure you could take is to refrain from touching your face when outdoors.

5. You can develop a poison ivy rash from touching objects and pets.

You don’t need to touch poison ivy to develop a poison ivy rash. Urishinol can easily be transferred to your skin by objects, such as garden gloves and clothing. It can also be carried around by dogs and cats, which pick it up when exploring the outdoors. And the tricky thing is, dogs and cats don’t appear to develop rashes from poison ivy. The oil just doesn’t bother them the same way it does most people. So while your family dog may seem perfectly fine, he could be passing the irritating oily substance to you when you pet or snuggle him.

6. Poison ivy urushiol has a long shelf life.

Urushiol takes a long time to break down. Sources vary in the exact amount of time the substance takes to break down, but an article published by Des Moines University states that it can last up to 10 years on a piece of clothing and continue to cause allergic reactions. For this reason, it’s important to wash the clothing and equipment that you use outside with soap and water.

7. Washing immediately with soap and water can help.

If you realize that you’ve touched a poison ivy plant, carefully wash that area of your skin with cold water and soap as soon as possible. This will remove the urushiol from your skin, which can lessen the severity of the rash. It will also prevent you from spreading the rash on other areas of your skin. The window of time you have to do this is small. After a few hours, it’s unlikely that washing with soap and water will help. However, washing will still remove the urushiol and prevent you from spreading the rash on other parts of your body.

8. Some poison ivy reactions require a trip to your doctor.

Many people treat mild poison ivy rashes at home, soothing the symptoms by taking lukewarm baths and applying cool compresses and itch-reducing lotions, such as calamine lotion. It’s important not to scratch the blisters, as bacteria from under your fingernails can cause infection.

If you have a severe reaction or have developed a poison ivy rash around your eyes, mouth or genitals, it’s important to see a doctor, according to the American Academy of Dermatology. A severe reaction might include swelling of the face or around the eyes, difficulty breathing, fever or itching that’s so bad it’s keeping you up at night.

Your doctor may prescribe an oral corticosteroid, such as prednisone, according to the Mayo Clinic. And if a bacterial infection has developed at the rash site, your doctor may give you a prescription for an oral antibiotic.

9. Don’t burn poison ivy.

If you’re getting rid of poison ivy plants growing on your property, do not burn them. Smoke inhaled from poison ivy can cause an allergic reaction that can cause difficulty breathing.

Instead, many experts suggest using herbicides to kill poison ivy. Specifically, herbicides that contain the active ingredient glyphosate and triclopyr work well, according to the UMass Extension.

A riskier method of removal would be to pull the plants up while wearing plenty of protective clothing and gloves, which you should throw away after. Don’t not use a chainsaw or string trimmer, which can easily splatter urushiol from the plant onto you.

Poison ivy is a plant that should be taken seriously, but in most cases, it can easily be avoided. When spending time outside, keep an eye out for “leaves of three.” And if in doubt, don’t touch the plant. “Leave it be.”

Aislinn Sarnacki can be reached at asarnacki@bangordailynews.com. Follow her on Facebook: facebook.com/1minhikegirl, Twitter: @1minhikegirl, and Instagram: @actoutdoors. Her guidebooks “Family Friendly Hikes in Maine,” “Maine Hikes Off the Beaten Path” and “Dog-Friendly Hikes in Maine” are available at local bookstores and wherever books are sold.

Aislinn Sarnacki

Aislinn Sarnacki is a Maine outdoors writer and the author of three Maine hiking guidebooks including “Family Friendly Hikes in Maine.” Find her on Twitter and Facebook @1minhikegirl. You can also...