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How to Avoid Poisonous Plants and What to Do if You're Exposed

Bob Bahlmann is the executive director of the education nonprofit Explore the Outdoors and has written a series on wilderness survival.

Forget-me-nots (not a poisonous plant).

Forget-me-nots (not a poisonous plant).

Don't Forget These Poisonous Plants: Sumac, Oak, Ivy

Forget-me-nots are delicate blue flowers that are supposed to help us remember those we care about. Although this is certainly romantic, we might be wiser to remember some other plants, those that might be encountered in the out-of-doors and can cause pain and discomfort.

A run-in with poisonous or otherwise painful plants can ruin an outing and discourage people from returning to the outdoors. In this article, we will learn about a different kind of “forget-me-not,” the kind you should be able to identify and avoid.

Unless a person is extremely allergic to one of these plants, contact with them is usually not life-threatening, but they can make you pretty miserable.

Additionally, many innocuous-looking plants are poisonous if eaten. While it's outside the scope of this article, good rule to follow is that you shouldn’t eat any wild plant unless you know for certain that it is safe.

Urushiol, the Potent Oil in Poisonous Plants

Let's first take a look at plants that actually have the word “poison” in their name. Poison ivy, poison oak, and poison sumac all secrete a fluid that irritates the skin of animals. The fluid is called urushiol oil and is very potent.

According to the Poison Ivy, Oak & Sumac Information Center, urushiol is so powerful that 1/4 ounce of this oil is enough to cause a rash on every person on earth. As many as 500 people could be itching from the amount of oil that would cover the head of a pin.

The oil can stay active for as long as five years, which means that even dead plants can cause a rash.

Sensitivity to urushiol can develop at any time. Even if you touched one of these plants and didn’t have a reaction, the next time you touch it, you might feel the pain.

Poison ivy rash on lower leg

Poison ivy rash on lower leg

Urushiol Causes a Painful, Itchy Rash

The rash from these plants can be spread if the oil is moved from one place to another. Contact with urushiol usually causes a painful, itchy rash that can develop blisters.

The rash from urushiol usually starts to develop in four to 12 hours but sometimes the rash won’t appear for days after touching the plants. That’s why it’s important to be able to identify these plants and wash the oil off as quickly as possible.

The oil can be easily washed off with water before it has a chance to be absorbed into the skin. Fast action can be the best treatment in avoiding a long-lasting, ugly, and painful rash.

If a rash develops you can ease the discomfort by applying calamine lotion, Epsom salts, or bicarbonate of soda. There is a vaccine, but it is only effective if taken before contact with the oil.

7 Poisonous Plants and How to Avoid Contact With Them

  • Whenever you will be outside in an area where these plants can be found, be sure to wear long pants, long-sleeved shirts, and fully enclosed shoes.
  • Gloves can help protect your hands.
  • When you get home, carefully remove your outer clothing and wash it right away. You can also apply a protective cream to your skin.
  • Sometimes pets will carry irritating oil on their fur. If you think your pets have been in poison ivy, oak or sumac, wash them off before petting them.
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Read More From Skyaboveus

Poison ivy.

Poison ivy.

1. What Is Poison Ivy, and How Do I Identify It?

This attractive plant is the most widespread of the urushiol oil-producing plants. It can be found all across Northern America.

  • Poison ivy usually doesn’t thrive above 5000 feet.
  • The old Boy Scout saying “Leaves of three, let it be,” certainly applies to poison ivy. These plants have what are called compound leaves. They are actually three small leaflets that are connected to a stem by a single leaf stalk. The center leaf of the three leaflets is usually longer than the other two.
  • The leaves are a shiny green during the growing season and can turn red, yellow, or orange in the fall.
  • When present, the berries will be white and waxy and grow along the stem. The plant can be an erect shrub or a low-growing or climbing vine. Poison ivy grows best along the edges of fields or heavy cover and does not seem to compete well against more aggressive types of plants.
  • Because it can be a climbing vine, poison ivy often has small aerial roots growing off the stem, giving them a fuzzy appearance.
Poison oak.

Poison oak.

2. What Is Poison Oak and How Do I Identify It?

Poison oak comes in both eastern and western varieties. The eastern version is found in the southeastern part of the United States.

  • Like poison ivy, poison oak has three leaflets, but they have the characteristic smooth lobes of the oak family.
  • The leaflets can be up to six inches long and usually turn yellow or orange in the fall.
  • It grows best in sandy soil.
  • The western variety is very common in California and is found only near the Pacific coastline. It prefers damp semi-shaded areas near running water.
  • Western poison oak can be hard to identify because it sometimes mimics the other plants around it. Contact with this plant is one of the most frequent causes of workman’s compensation claims in California among people who work in the outdoors.
Poison sumac

Poison sumac

3. What Is Poison Sumac and How Do I Identify It?

Poison sumac is a shrub or small tree that grows in wet soil such as swamps and peat bogs in the eastern United States.

  • Unlike poison ivy and poison oak, poison sumac has more than three leaflets, usually anywhere from seven to 13 on a central stem. The leaflets are from two to four inches long.
  • In the fall, poison sumac leaves can turn a wide range of bright colors ranging from yellow to purple. The plant can be as tall as 20 feet.

KISS: Keep It Simple Sweetie

This video had some good tips and some product endorsements. I especially liked the recommendation to use dish soap to remove the oils. KISS: Keep It Simple Sweetie.

4. What Is Wild Parsnip and How Do I Identify It?

Wild parsnip is not native to the United States but has been found here for over 100 years.

  • It has feathery leaves, hollow stems with irregular grooves, and flat-topped yellow flower clusters from mid-summer to early fall.
  • It is considered an invasive species that most people would like to eliminate. These plants secrete a fluid that causes phytophotodermatitis, a burn caused by the fluid making your skin extra sensitive to the ultraviolet light from the sun.
  • If a human brushes against the plant or comes in contact with its sap, the fluid is absorbed by the skin. These chemicals are then energized by ultraviolet light, causing the skin tissue to break down, leaving a red area similar to a sunburn.
  • The pain and irritation caused by wild parsnip usually go away in a day or two, but discoloration of the skin can last a year or more.
  • If exposed to wild parsnip, wash the affected area as soon as possible. If you are going to be around the plants, wear long pants, long-sleeved shirts, and gloves.
Wild parsnip.

Wild parsnip.

5. What Is Stinging Nettle and How Do I Identify It?

This plant is found across the United States, usually growing in moist soil and disturbed ground.

  • It is a perennial plant between 2-4 feet tall. It has a four-sided stem and fringed leaves.
  • The flowers are small and green.
  • The plant has tiny rigid hollow hairs that work like a hypodermic needle to inject histamine and other chemicals. These chemicals result in a sting causing an initial itching and burning and usually a welt. Sometimes within minutes, sometimes hours later, the stinging turns into a tingling, somewhat numb sensation.
  • The best way to relieve the irritation is to apply a cream with an anti-histamine or hydrocortisone. Some people believe that applying mud, saliva or baking soda will bring relief to the affected area.
  • Stinging nettle looks similar to wild mint. If the plant has tiny hairs on it, don’t touch it.
Stinging nettle.

Stinging nettle.

6. Other Thorns, Spines, and Prickles

Thorns, spines, and prickles are similar because they are plant parts that are hard and pointed, but they are different.


These are modified branches or stems. They develop from buds either at the end of branches (terminal bids) or in places where a new branch might start to grow (axillary buds).

Thorns are used for defense, keeping animals from eating the plant. Some examples of plants with thorns are citrus trees, Russian olive, and pomegranate.


Spines are either modified leaves or parts of leaves. Because of this, they grow in places where you would expect a leaf to grow. They help the plant reduce moisture loss. A good example of this is the common cactus.

Thistles have spines all along their leaf margins. This protects the plant from being eaten.


Prickles grow from the bark of plants and are not extensions of branches or leaves. They grow in irregular patterns at any location along the stem.

Because they are not a part of any plant organ, they have no real connecting tissue to the plant and can be can easily broken off the stem. The most familiar plant with prickles is the common rose.

The common rose has prickles.

The common rose has prickles.

Fun Fact

There’s a famous saying that goes like this: “A rose by any other name is still a rose.” It’s also true that it doesn’t matter how many times you call the pointy thing on a rose stem a thorn, it’s still a prickle.

Activity: A Prickly Situation

The pictures below show some pointy plants. See if you can figure out if the sharp parts are thorns, spines, or prickles. Look closely for the clues you’ve been given and don’t feel too bad if you don’t get them all correct.

The answers are below the pictures.

Answers: 1. Thorn 2. Spine 3. Prickle 4. Spine 5. Thorn 6.Thorn 7. Spine 8. Prickle

Answers: 1. Thorn 2. Spine 3. Prickle 4. Spine 5. Thorn 6.Thorn 7. Spine 8. Prickle

First Aid for Thorns, Spines, and Prickles

Although these pointy protrusions don’t inject poison, they can be painful, difficult to remove, and cause infection. Thorns and prickles are usually large enough they can be removed in the same way you would remove a splinter.

With a sterile pair of tweezers, grab the protruding part of the thorn and pull it out. Apply an antibiotic ointment and a band-aid if needed.

Removing spines can be more challenging. Many have barbed ends, like those found on a cactus. Still, the best way to remove large spines is with tweezers as described above.

Many spines are very small (called glochidia) and not only difficult to see, but hard to get hold of with tweezers. Some people try to bite or suck them out. This might result in getting them stuck in your lips or tongue.

Tests conducted on rabbit skin showed that gently spreading a thin layer of household craft glue over the affected area, laying a thin piece of gauze into the glue and allowing it to dry, and then peeling off the glue/gauze combination would remove more than 60 percent of imbedded glochidia.

By repeating the process, more can be removed until they’re all out. When you’re finished, apply an antibiotic ointment.

7. Marijuana, a Different Kind of Dangerous

There is another dangerous plant you should be aware of as you venture into the outdoors. Unfortunately, there are unscrupulous people who are taking advantage of the remoteness of the backcountry for illegal activities that rob us of our right to enjoy the outdoors.

In 2008, over four million marijuana plants were seized in California alone. Most of these pot farms are run by the big drug cartels. Since these fields are worth millions of dollars, they are sometimes protected by armed guards who will defend their crops with force.

Being able to identify a marijuana plant can help target pot farms, but it’s usually the farm itself that gives these operations away.

The growers will clear away most of the trees but still leave enough to hide their plants from the air. They will clear ground cover to keep it from competing with the young marijuana plants. They will run pipes from water sources to their crops and they will live near enough to watch over their cash crop.

Anything that looks like a long-term camp in the backcountry could be the abode of pot growers. If you see any of these signs of marijuana farms your first concern should be your own safety. Make note of the location of the site, preferably with GPS coordinates, and get away as soon as possible (warn others to stay away, too).

This content is accurate and true to the best of the author’s knowledge and does not substitute for diagnosis, prognosis, treatment, prescription, and/or dietary advice from a licensed health professional. Drugs, supplements, and natural remedies may have dangerous side effects. If pregnant or nursing, consult with a qualified provider on an individual basis. Seek immediate help if you are experiencing a medical emergency.

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