Many years ago, I had just bought my first home and, as you might expect, was really excited to get out into the garden and make it my own. The backyard was overgrown with English ivy, so I spent an entire day pruning it back and hauling armloads off the property. Around midnight that evening, I was miserable. I had been so eager to transform my landscape, I hadn’t even noticed the poison ivy tangled in with the English ivy – until hours later when my whole body was covered by a severe reaction.
I went to the ER about two hours later and was told by the nearby Atlanta hospital that I had the worst case of poison ivy the staff had seen all year. It was the end of August. Since that time, I do everything possible to avoid this pernicious vine, and if you’ve ever experienced the effects of poison ivy, you probably take great pains to avoid it too.
Around 80% of us are allergic to urushiol – the compound in poison ivy that causes the burning, itching rash. Sensitivity varies from person to person between the relatively mild to the life-threateningly severe.
Unfortunately, this poison ivy is just about everywhere, and urushiol is present in many more plants than you probably realize. So, I invited Dr. Susan Pell, a botanist with a Ph.D. in plant biology, to join me for this episode to help us all better understand poison ivy and how to avoid and treat it.
Susan is currently the Executive Deputy Director at the U.S. Botanic Garden in Washington D.C. Her doctorate thesis research focused on the molecular systematics of the cashew family of plants. So, why would I ask an expert on the cashew family to give us the dirty details on poison ivy? Well, poison ivy is one of 800 plant species from all over the world which belong to the cashew family.
Cashew Family of Plants
Do you love mangos? Did you know they’re related to poison ivy? Mangos, pistachios, sumac, smoke bush, even pink peppercorns – all are members of the very diverse cashew family, and all of them contain urushiol in at least some of their plant parts.
You can buy most types of nuts in both shelled and unshelled form, but you won’t see unshelled cashews at the supermarket. That’s because the fruit and shell of cashews contain urushiol and can cause dermatitis – just like poison ivy. If you’ve ever noticed small, hard black bits stuck to the cashews you buy, that black material is actually urushiol which has oxidized. It’s usually the less-expensive cashew products which contain the bits of urushiol, so Susan suggests paying a little bit extra for higher-quality cashews.
If you’re like me and experience a severe reaction to poison ivy, Susan recommends that you avoid the peppercorn mixes sometimes available for sale too. Black, white and green peppercorns don’t contain urushiol. It’s only the pink peppercorns which can cause a painful reaction on your lips and in your mouth, and it’s a variety often included in peppercorn mixes.
As for the poison ivy plant, it’s found throughout every state in the U.S. except California. The species has been found occasionally in The Golden State, but in general, poison ivy doesn’t do well in the Mediterranean-like climate of California. There are plant species in the northern areas of California which will interbreed with poison ivy, but residents of the state are more likely to deal with poison oak, instead.
Poison oak is closely-related to poison ivy and is another member of the cashew family, so the urushiol in its foliage, stems and berries can cause an equally severe reaction.
Learn to Recognize Poison Ivy
We’ve all heard the saying “Leaves of three, let it be.” A trio of leaves is one of the first indicators of poison ivy. In fact, all the plants of the cashew family share the common characteristic of compound leaf form – multiple leaflets which extend from a central stem or petiole.
The leaf form of poison ivy is one terminal leaflet above two lateral and opposite leaflets on a single stem. That group of leaflets is considered a single leaf, and those grow up the vine of poison ivy in alternating order. In other words, a three-leaflet leaf on the right side of the vine, and the next one further up the vine on the left side.
Those leaves are wavy along the margins and pointed with just a slight rounding at the tip. The vine itself is a climber with a woody trunk, and you’ll usually find red, adventitious roots (roots which sprout from parts of a plant other than the root zone) extending out all along the trunk.
There tends to be small black spots on poison ivy foliage. That’s actually the urushiol compound which has oozed out of the leaf through some sort of cut and oxidized. The leaves vary in size from around an inch up to several inches in length, and they turn a brilliant red in fall.
This species loves to grow in areas which have been disturbed. That’s why you’ll often see it at the edge of a cleared forest or a hiking trail. Once an area has been disturbed, it doesn’t take long for poison ivy to move in, and it can quickly outcompete other plants for the space.
A Prolific Spreader
So, how does poison ivy make its way to a newly-disturbed surface? One method is its seeds, which spread for miles in the bellies of birds. Actually, lots of wildlife love the white, cream-colored and red berries of this plant. The seeds in the berries pass through the digestive system of the bird or animal and germinate easily once they’ve made contact with soil and have access to light.
Animals, birds and other creatures don’t feel the irritating effects of the urushiol. There are a few primate species which will experience a reaction, but it’s the 80-85% of the human species most likely to feel the negative side effects.
Once poison ivy has germinated and begins to mature, it also develops a rhizome system. It’s the rhizomes which really make poison ivy difficult to eradicate in the landscape. A rhizome is a horizontal stem which grows underground and sends out lateral shoots. Even a tiny piece of rhizome left behind in soil is capable of producing a new poison ivy vine.
There was an interesting study done by Duke University recently. The research sought to determine the impact of climate change on poison ivy in North Carolina. It was found that as CO2 levels increased, so did the growth of the plant. That’s not a big surprise since all plants need and take in CO2 and expel oxygen.
What was surprising was that CO2 levels also affected the urushiol. Increased CO2 caused the urushiol to become more potent, and it caused the compound to bind more strongly to skin cells. Translation: It became more virulent.
The Facts on Urushiol
As a horticulturist, I believe that every plant has some purpose. Poison ivy is no exception. For one thing, those berries provide an important food source for many beneficial creatures. The foliage is a food source for many grazing animals and for a number of insects, which eat the leaves during their larval stage.
So, why does this plant – along with other species of the cashew family – produce urushiol? This compound, which is toxic to most humans, serves as an anti-microbial, anti-bacterial and anti-viral protection for the plants. It serves to protect them from disease.
Urushiol is extremely persistent in the environment. In fact, Susan has found that it can remain active for up to a century – at least. Think about that for a moment. Urushiol in pieces of poison ivy which have been dead for 100 years still has the potency to cause dermatitis. If only some of the more pleasant characteristics of the plants we love were so long-lived.
Unfortunately, it doesn’t matter if the vine has died in your landscape or is dormant in the dead of winter. That urushiol is still going to get you. It will get you from any and every part of the plant too – leaves, berries, roots – the whole enchilada. So, take precautions.
Urushiol doesn’t just persist in the plant either. Any tools, gloves, clothing, etc. that comes into contact with the compound is a rash just waiting to happen – until you clean them thoroughly. That’s why, when she’s handling poison ivy, Susan only wears gloves which are machine-washable or disposable.
Any tool you use to cut away or move poison ivy will still be covered in urushiol. So, it’s important to clean your tools just as soon as the job is done. Otherwise, the compound will be waiting patiently active to make you miserable as soon as you touch it – even months later and after storage through the coldest of winters.
Urushiol transfers from surface to surface, so anything that you touch after touching poison ivy will need to be cleaned too. Did you take off your sunglasses? Those will need to be wiped down. Did you drive home after accidentally handling the vine on a hike? Think about your car keys, steering wheel, door handle, etc. The urushiol that was on your hands can transfer to and remain on any of those surfaces.
The Dreaded Reaction
It’s possible that you are among the lucky 15-20% of people who aren’t allergic to urushiol, but don’t bank on it. The first exposure tends to generate very little, if any, reaction. It’s each exposure afterward which makes you more susceptible.
Sometime after contact with the plant, the urushiol compound binds to the protein in skin cells. The dermatitis reaction comes as a result of our immune system attacking the cells which the compound bound itself to. Each time urushiol binds itself to your skin, your immune system learns to react more quickly and more intensely.
As your immune system tries to kill the affected skin cells, the cells become inflamed. Along with the inflammation comes the itching, burning and puss-filled blisters.
The reaction occurs within a couple of hours of exposure or can be delayed as long as ten days. The timeline varies for everyone and depends on individual sensitivity, which depends – in part – on frequency of exposure.
I can remember rolling in poison ivy as a kid, and I never had a reaction. It wasn’t until years later, on that fateful day pulling English ivy, that my immune system let me know that it wasn’t going to tolerate urushiol after all.
There are rumors out there that exposing yourself to poison ivy will help you build up immunity to the allergy. That’s actually a fairly dangerous myth, because the opposite is true. The more you expose yourself, the more virulently your immune system will react. So if the discomfort isn’t enough to keep you away from poison ivy, hopefully the thought of increasingly severe reactions will be.
Sometimes, we have no choice but to deal with poison ivy in our landscape. When that’s the case, take this plant seriously, and protect your skin with the proper gear – including gloves and long sleeves.
There are some products available which you can apply to your skin to form a protective layer, like sunscreen or insect repellent. Ivy Block and Ivyx are two examples. These are lotions you put on your skin before working with poison ivy. The urushiol compound binds to the Ivy Block or Ivyx rather than your skin cells.
If you forget to apply a preventative product or if you make contact with poison ivy unexpectedly, remember that there is a delay between contact and when the toxic compound binds itself to your skin cells. That delay is your window to head off a reaction.
Wash the area of contact and any part of your body where you might have transferred urushiol after making contact. Sweat can transfer urushiol too, so your safest bet is to take a shower.
Because urushiol is an oil, it’s best to wash with cold water to minimize the spread. Use plenty of soap to break down the oil and wash all traces down the drain. You might have heard that Dawn soap is the most effective at washing off urushiol, but Susan says that any soap will do.
If you can’t wash, be sure to have a post-exposure product, like Technu, on hand. Tecnu circumvents a reaction by breaking the bond that urushiol makes with the proteins in our skin cells. When the compound doesn’t bond to your skin, your immune system doesn’t recognize a need to react. Just remember that you need to be thorough and apply a post-exposure product to any area of your skin that urushiol may have transferred to.
Be sure to wash all the clothes you were wearing and any tools you were using or other items you were carrying. As you remove your clothes or handle tools to clean them, you might be re-transferring the urushiol oils, so you’ll need to wash again or re-apply a post-exposure treatment.
Even your pets can be the oil-transferring culprit. Pets won’t experience a reaction themselves, but the compound can remain on their fur and transfer to your skin when you pet them. Honestly, you just can’t be too careful with this stuff.
How long do you have between the time of contact and when it’s too late to wash it off? That varies from person to person, and remember, that window can change as you experience more incidents of contact. So, the sooner you can clean up, the better.
Once you have washed, you can’t spread poison ivy to something – or someone – else. Even if you experience a reaction, it’s not contagious. The rash doesn’t contain urushiol, it’s your body’s response to the compound having bound to your skin cells before you washed.
If you are one of the unlucky souls to experience a severe poison ivy reaction, you would be wise to become familiar with other members of the cashew family. Many of those plant species can bring on a rash just like the pink peppercorns Susan warns us about.
For example – there’s another species, known as poisonwood, which grows in the Everglades of Florida. The sap of sumac and smokebush can cause a reaction in some people too. The risk varies across the cashew family from plant to plant and person to person.
Getting back to those mangos – lots of us love the fruit; but the leaves, bark and even the skin of the fruit can cause dermatitis. So, it’s a good idea to avoid eating the flesh of a mango directly off the rind, or you could be training your immune system to go on the attack against urushiol.
Poison Ivy Treatment
When you do experience a rash, treatment depends on the intensity of your body’s reaction. There are over-the-counter corticosteroid creams available, but the rash can be so severe that you might need to see a doctor to treat the inflammation with a prescription steroid. You might also be given an antibiotic to prevent the blistering on your skin from becoming infected.
Steroids will promote quicker healing of your skin, but other treatments you may have heard about are only good for soothing some of the discomfort.
Calamine lotion, for example, will help to dry out the blisters. That will make you a bit less uncomfortable, but it won’t speed the healing. Any over-the-counter product designed for itch relief might help you make it through the day – or to get some sleep.
Have you heard that jewelweed is an effective poison ivy treatment or even a preventative? It does have some anti-inflammatory properties, but it won’t help you avoid a reaction – nor will it heal a rash any quicker.
Removing Poison Ivy
We don’t have control over the birds or other wildlife which bring poison ivy seeds onto our property, so there is no way to prevent it from encroaching. When you learn to correctly identify it, you can act quickly.
It’s easier to remove a young plant than an established one. Although I always recommend physical removal as the best option for any weed or other unwanted plant, it’s just not an effective approach for poison ivy – at any stage.
I avoid herbicides at all costs at the GardenFarm, and Susan turns to them only as last resort as well. Unfortunately if even a small section of poison ivy rhizome is left behind in the soil, it will regrow into a new plant. That means poison ivy is so pervasive that Susan feels herbicides are necessary for removal of this particular landscape foe.
Always read and follow the instructions on the label of an herbicidal product carefully, and to minimize the unintended consequences of using these products, Susan recommends painting it directly onto the leaves of the plant. If you are dealing with a large, established vine; cut it near its base. As long as the rest of the vine isn’t making contact with soil, it will die back.
You’ll still need to deal with the vine base and roots. To prevent it from resprouting, drill a hole into the base and fill it with the herbicide product. The targeted application of herbicide will kill the base and the roots.
Whatever you do, never burn any part of the poison ivy plant. Urushiol can become airborne, and the reaction from inhaling it can be lethal. Wildlife firefighters are always at risk of breathing in urushiol, and according to Susan, 15% of the worker’s compensation budget for the State of California goes to treat firefighters who have inhaled poison ivy’s equally toxic cousin – poison oak.
That’s just further proof this is a category of plant that we should all take seriously.
You’ve learned my worst poison ivy story. What’s yours? Please share it in the Comments section below. Your story might help someone else to avoid the misery of exposure.
I hope this week’s podcast has cleared up some facts on poison ivy and that it will help you to avoid any future painful reactions. Be sure to listen in to my conversation with Susan by clicking the Play icon in the green bar under the page title. She shares a few interesting stories of poison ivy striking in some unusual and unexpected ways.
Links & Resources
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