Poison Ivy and Other Plants: What To Know

Medically reviewed by Daniel More, MD

Poison ivy is a poisonous plant that can cause a skin rash in people who come into contact with its leaves, stems, or roots. The medical name for this rash is contact dermatitis or Rhus dermatitis. The rash is actually an allergic reaction to an oil called urushiol produced by the toxic vine. This resin can be found not only in poison ivy but also in poison oak and poison sumac plants.

The hallmark poison ivy rash is red, itchy, and swollen and can also have hives or blisters. You'll likely know what it is when you see it, although a healthcare provider can tell you if the rash is caused by something else. Most cases of poison ivy rash go away within a couple of weeks.

It only takes a tiny amount, less than one grain of table salt, to cause a reaction. Around 80% to 90% of people will develop this rash if they come into contact with the urushiol. Read on to learn about poison ivy, including pictures and how to treat it.

Related: When Does an Animal Bite Warrant a Trip to the ER?

What Do Poisonous Plants Look Like?

It's important to be able to identify poisonous plants, which often change depending on the type and season. Poison ivy and oak, for example, typically have three glossy leaflets that grow on each leaf. This trait gave rise to the famous warning phrase, "Leaves of three, let them be." Poison sumac, in contrast, usually has seven to 13 leaflets. These poisonous plants can also change based on the season.

Poison Ivy

Poison ivy grows either as a vine or as a shrub in most parts of the United States, with the exception of Alaska, Hawaii, and certain areas along the West Coast. How can you tell if it's poison ivy? The leaflets can be rounded or have multiple jagged edges and change color depending on the season. The leaves are reddish in the spring and green in the summer. You'll notice the leaves are yellow, orange, or red in the leaves.

The plants sometimes have black dots, which is urushiol. Poison ivy may sport berries—yellowish white, orange, red, or yellowish green, depending on the season.

Poison Oak

Poison oak, like poison ivy, typically has three leaflets that grow on each leaf. These shiny leaves are usually green in the summer and red or yellow in the fall. You might find green or yellow flowers and greenish-yellow or white berries on the plant. Poison oak grows as a shrub in the Eastern and Southern United States or in vines on the Pacific Coast.

Poison Sumac

Poison sumac can grow as tall shrubs or small trees in bogs or swamps. You'll usually find this poisonous plant in the Northeastern, Midwestern, and parts of the Southeastern United States. There are typically seven to 13 smooth leaflets on each leaf.

These leaves are orange in the spring, green in the summer, and then become orange, red, or yellow in the fall. Some poison sumac plants have green or yellow flowers and greenish-white fruits.

Poison Ivy Rash Symptoms

The hallmark sign of poison ivy is an itchy rash that can develop blisters that break open and crust over. The rash may show up within a few hours or develop two to three weeks after contact with poison ivy. A poison oak and sumac rash will look the same because the urushiol oil is the culprit.

People typically experience poison ivy rash symptoms in stages, which include:

• Itching: The first sign is typically intense itching on the area of the skin where the rash later forms.

• Rash: You will then develop a raised, itchy red rash where your skin has touched urushiol oil. People with darker skin may notice a dark purple or brown rash. The rash may show up in patches, lines, or streaks, which follow where the poison ivy comes in contact with your skin.

• Blisters: Some people develop fluid-filled blisters, especially if the rash is severe. These blisters break open and ooze.

• Crusting: The blisters will eventually crust over and continue to itch.

Do not be surprised if the rash looks different on various parts of your body at different times. This is normal and does not necessarily mean the rash is getting worse.

How Is Poison Ivy Diagnosed?

You generally do not need to see a healthcare provider to diagnose poison ivy. Most cases of poison ivy are obvious by looking at the rash and knowing or suspecting you have come into contact with foliage. A healthcare provider, particularly a dermatologist, can provide a more definitive diagnosis. The dermatologist can also help rule out other causes if necessary.

You might need to see a dermatologist under some circumstances. It's essential to get medical help if you develop severe symptoms or if the rash spreads to your face or genitals.

Contact a healthcare provider or go to the ER if you have:

• A fever over 100 degrees

• A rash that covers more than a quarter of your body

• A swollen tongue or throat

• Itching that keeps you up at night

• Signs of a skin infection (e.g., pus, soft yellow scabs, or tender skin)

• Trouble breathing

Treatment

A poison ivy rash usually goes away on its own. Make sure you rinse your skin right away. Use rubbing alcohol, poison plant washes, degreasing soap (e.g., dishwashing soap), and a lot of water. Scrub under your nails with a brush. Urushiol from a plant can spread if you touch the oil with your fingers and then touch another part of your body.

Home remedies for a poison ivy rash that help alleviate itching include:

• Pressing a damp, cool compress on the itchy area

• Soaking in a soothing colloidal oatmeal bath 

• Trying one of many OTC products that help tame the itch (e.g., calamine lotion or hydrocortisone cream)

• Using oral antihistamine pills like Allegra (fexofenadine) or Benadryl (diphenhydramine)

A healthcare provider can prescribe a stronger steroid ointment or an antibiotic if you have signs of an infection. These include swelling, pain, pus around the rash, or a rash that is warm to the touch.

It's hard to know how long symptoms from poison ivy will last. It usually depends on how sensitive your skin is and how much oil gets on it. A poison ivy rash that lasts up to 21 days is not unusual, especially if you have never had one before. On the other hand, people who have had previous rashes will see a rash go away within one to 14 days.

Prevention

You can take several precautions to prevent contact with a poisonous plant. Here are some ways to prevent a poison ivy rash:

• Clean tools or other objects: Use rubbing alcohol or soap and water. Wear disposable gloves while you are cleaning. This protects your hands from picking up any urushiol on the items.

• Steer clear of poison ivy: Learn how to identify the plant if you are going outdoors and think you might come into contact with poison ivy. You might also want to teach any children you are with how to identify poison ivy.

• Use an ivy blocker: This cream acts as a buffer between urushiol oil and your skin. The active ingredient in these creams is bentoquatum, which acts as a shield to protect the skin from the oil.

• Wear protective clothing: This includes long pants, long sleeves, gloves, and boots. Wash the clothes you have worn separately in hot water with detergent if you are exposed.

How To Get Rid of Poison Ivy Plants

You can get rid of poison ivy plants yourself or hire a professional to do it for you. Make sure you can accurately identify the plant if you do it yourself. Wear thick gloves, boots, long sleeves, and pants to make sure your skin does not come into contact with the plant.

You can pull poison ivy out of the ground like a weed, but make sure you get the roots. Some people also use an herbicide. Bear in mind that you can still get poison ivy rash from dead plants.

Never burn poison ivy. Smoke from the burn contains urushiol oil and is very harmful if you inhale it. This can cause a severe allergic reaction and make breathing difficult. The smoke can affect anyone in the direct vicinity of the fire and even people who are far downwind.

Once you are done, wash all your clothes and anything that may have come into contact with the poison ivy. Make sure you wash yourself, especially your hands. Scrub under your nails, even if you have been wearing gloves.

Related: What Is a Wasp Sting?

A Quick Review

There's a good chance you will not forget it if you have had a poison ivy rash once. The blisters and itchiness can be very uncomfortable.

You can do several things to prevent getting urushiol from poison ivy on your skin. Know how to identify poison ivy. Wear clothes that cover your skin. Use a barrier cream if you think you'll be in an area with poison ivy. Carefully remove and launder any clothing, and wash your skin with soapy water after spending time in places where you might find poison ivy growing.

FAQs

Frequently Asked Questions

1. How long after touching poison ivy does it appear?

A small percentage of people are immune to urushiol oil and would not know if they had a close encounter with poison ivy. Others will certainly know it, though perhaps not right away.

Symptoms can take hours, days, or even two to three weeks to appear. How quickly symptoms develop depends on how much urushiol oil comes into contact with your skin and whether you have had a previous rash.

2. Is poison ivy contagious?

You cannot get poison ivy from another person unless they still have urushiol on their skin. This is unlikely, though, since the skin absorbs the oil very quickly.

You can spread poison ivy on your own body if the oil is still on your fingers or under your nails, and you then touch other body parts. Washing and rinsing your skin after you have come into contact with poison ivy can stop the oil from spreading.

3. Can you get a poison ivy rash from a dog or cat?

There's a danger of getting a poison ivy rash from dogs and cats that have urushiol on their fur. Be careful when touching your pet after they have been rollicking in the woods. You'll want to wash your dog or cat before checking for ticks if you suspect they have been in contact with poison ivy.

Wearing rubber gloves and goggles can protect you from droplets containing urushiol in case your pet shakes off the water. Throw any towels you use to dry them in the washing machine, and let your pet dry off fully before petting. Wash your pet's leash, collar, and any other objects that may have urushiol on them.

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