What Is Poison Ivy?

A typical poison ivy rash is red, itchy, and swollen, and can also have hives or blisters.

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

Around 80% to 90% of people will develop this rash if they come into contact with the urushiol, says the Centers for Disease Control and Prevention (CDC). And it only takes a very smally amount of urushiol, less than one grain of table salt, to cause a reaction.

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 your healthcare provider can tell you if the rash is caused by something else. Most cases of poison ivy rash go away on their own within a couple of weeks. Over-the-counter (OTC) creams and lotions can help ease the itch. In rare cases, poison ivy can cause more serious complications that may require medical treatment.

Here's what to know about poison ivy rash, the plant that causes it, and how to treat it.

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Signs and Symptoms of Poison Ivy Rash

A small percentage of people are immune to urushiol oil and wouldn't know if they had a close encounter with a poison ivy plant. The other 80% to 90% will certainly know it, though perhaps not right away. Evidence that you've tangled with poison ivy can take hours or days to appear, depending on how sensitive you are and how much urushiol oil came into contact with your skin.

The main sign of poison ivy is a raised red rash where your skin has touched urushiol oil. The rash may show up in patches, lines, or streaks, which follow where the poison ivy came in contact with your skin. A poison ivy rash is usually also accompanied by swelling, hives, and bumps or blisters that can be either large or small.

A few days after they first appear, the blisters can crust and burst, letting loose a clear liquid. The rash may show up on different parts of the body at different times depending on how much oil came in contact with that particular area of the skin.

In more severe cases, poison-ivy rash can spread to your eyes, mouth, or genitals, and blisters may get infected with pus. Direct contact with the plant in any of these very sensitive areas can cause a rash, but you can also pick up the oils indirectly. For example, if the can or bottle you're drinking out of has come into contact with poison ivy and you drink from the container, you can get urushiol in your mouth.

Smoke and soot from burning poison ivy can be dangerous. If you've inhaled urushiol smoke or soot, you may have trouble breathing. The CDC recommends getting medical help if your symptoms are severe or or the rash spreads to your face or genitals.

Symptoms in milder cases:

  • Raised red rash
  • Swelling
  • Hives
  • Bumps or blisters
  • Itchiness

In more severe cases:

  • Difficulty breathing
  • Eyes swollen shut

Signs and symptoms of poison ivy should usually resolve within a few weeks. Anything longer than this probably requires a trip to your healthcare provider.

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What Causes Poison Ivy Rash?

A poison ivy rash is caused by urushiol oil from a poison ivy plant coming into contact with skin. The skin quickly absorbs the oil, which then causes the hallmark rash. Contact with any part of the poison ivy plant—the roots, stem, or leaves—can cause this rash.

You can come into contact with this irritating resin either by touching a poison ivy plant directly, or indirectly by touching an object that has oil on it, such a gardening tool, a piece of clothing, a pair of shoes, or a pet's fur. And if you inhale smoke from burning poison ivy, you can experience a severe reaction in your respiratory passages.

Urushiol oil doesn't stay on the skin for very long, but the CDC says it can stay on objects for as long as five years. This means you can easily develop a rash after touching anything that has urushiol oil on it.

If the oil is still on your fingers, you can spread the rash to other parts of the body. However, you usually cannot get the rash by touching another person who has touched a poison ivy plant because the oil is quickly absorbed into the body. You also cannot get a rash from liquid out of a burst blister.

In some cases, you can inhale urushiol particles—or get them on your skin—from poison ivy plants that are burning nearby.

What Poison Ivy Rash Looks Like

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Poison ivy rash can appear anywhere your skin has come into contact with the plant. The rash is red and can be irregularly shaped, or can appear as a line or streak. (Essentially, the rash will be an imprint of where you brushed against leaves or any other part of the plant.) It's usually accompanied by swelling, hives, and bumps or blisters.

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A few days after the rash first appears, the blisters will crust over and burst, releasing a clear liquid.

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The rash may appear on different parts of the body at different times depending on whether that area touched a little or a lot of oil. In severe cases, the rash can spread to your eyes, mouth, or genitals. If this happens, contact your healthcare provider.

How To Identify Poison Ivy

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Poison ivy grows either as a vine or as a shrub in most parts of the U.S. with the exception of Alaska, Hawaii, and certain areas along the West Coast, according to the U.S. Food and Drug Administration. The plant is known for the three glossy leaflets that grow on each leaf, a trait that gave rise to the famous warning phrase, "Leaves of three, let them be."

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The leaflets can be rounded or have multiple jagged edges, and they change color depending on the season. In the spring, the leaves are reddish. In the summer, they will be green. And in the fall they could be yellow, orange, or red. Sometimes the plants may also have black dots (this is urushiol). Poison ivy may sport berries—yellowish white, orange, red, or yellowish green depending on the season.

How Is Poison Ivy Rash Diagnosed?

Most cases of poison ivy are obvious just by looking at the rash and knowing or suspecting that you have come into contact with foliage. The rash will be red, swollen, and itchy and usually has hives and small or large bumps or blisters. The blisters usually last a couple of days before they burst, giving off a clear liquid.

Don't be surprised if the rash looks different on various parts of your body at different times. This is normal and doesn't necessarily mean the rash is getting worse.

A healthcare provider, particularly a dermatologist, can provide a more definitive diagnosis. The dermatologist can also help you rule out other causes.

Poison Ivy Treatment

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There is no cure for poison ivy rash. It will usually go away on its own, even if you do nothing. But you'll probably want to do something for the bothersome itching. Fortunately, there are treatments to relieve this and other symptoms.

If you think you may have come in contact with poison ivy, rinse your skin immediately. The CDC recommends using rubbing alcohol, poison plant washes, degreasing soap (like dishwashing soap), and lots of water. You may also want to scrub under your nails with a brush.

If you develop a rash, don't scratch it. Instead, try one of many OTC products that are available to tame the itch, such as calamine lotion or hydrocortisone cream. The CDC also says oatmeal baths may help you feel less itchy. Oral antihistamine pills like Allegra (fexofenadine) or Benadryl (diphenhydramine) can also reduce itching and may help you sleep.

Contact your healthcare provider or go to the ER for any of the following reasons:

  • You develop a temperature over 100 degrees
  • The rash spreads to your genitals, eyes, or mouth
  • You have trouble breathing
  • Your tongue or throat starts swelling
  • The rash covers more than a quarter of your body

And if your rash doesn't show signs of abating after a week or 10 days, you'll also want to contact your healthcare provider. Your healthcare provider may prescribe a stronger steroid ointment and, if you have signs of an infection (swelling, pain, pus around the rash, or a rash that is warm to the touch), an antibiotic.

Poison Ivy Rash Home Remedies

Simple home remedies can help ease itch from a poison ivy rash. Bathing in cool water can be a huge help, as can pressing a damp cloth (make sure it's cool as well) on the itchy area for 15 or 30 minutes at various times throughout the day.

Avoid hot water, as that can worsen the rash. But a soothing oatmeal soak may do the trick. You can take a soak in a colloidal oatmeal bath (you can make your own or buy a product at the drug store). Some experts recommend easing blisters with a solution of one or two Dome-Boro tablets (available at most drug stores) dropped in a pint of water.

Poison Ivy Rash Medications

  • Calamine lotion to relieve itch
  • Hydrocortisone cream to relieve itch
  • Oral antihistamines such as Benadryl to relieve itch
  • Antibiotics to heal a bacterial infection around the rash
  • Steroids in more severe cases to reduce swelling, redness, and itching

How Long Does Poison Ivy Rash Last?

It's hard to know how long symptoms from poison ivy will last. It usually depends on how sensitive you are and how much oil got on your skin. If your skin is sensitive, symptoms may take longer to clear. A poison ivy rash that lasts one to three weeks is not unusual.

The first signs (red, swollen, itchy skin along with blisters) can develop hours or days after first contact with a poison ivy plant. A few days later, the blisters will get crusty and drop off.

A poison ivy rash may also show up on different parts of your body at different times depending on how much urushiol oil landed on certain areas. The skin usually absorbs the oil quickly, but it can linger on objects for years. If your rash doesn't go away in a couple of weeks, contact your healthcare provider.

Is Poison Ivy Contagious?

You can't get poison ivy from another person unless the person still has urushiol oil on their skin. This is unlikely, though, since skin absorbs the oil very quickly. You can also spread poison ivy on your own body if oil is still on your fingers or under your nails and you then touch other parts of your body. Washing and rinsing the skin after you've come into contact with poison ivy can stop the oil from spreading.

There is a danger of getting a poison ivy rash from dogs that have urushiol oil on their fur, or inanimate objects, where urushiol oil can hang on for years. These objects can include clothing, shoes, gloves, garden tools, your dog's leash, and more. If you suspect an object has urushiol oil on it, clean it with rubbing alcohol or soapy water.

Be careful when touching your dog after it has been rollicking in the woods. If you suspect your dog has been in contact with poison ivy, you'll want to wash your pup before checking for ticks. Wearing rubber gloves and goggles can protect you from droplets containing urushiol in case your dog shakes off the water. If you dry your dog with a towel, throw it in the washing machine and let your dog dry off fully before petting. You should also wash your dog's leash, collar, and any other objects that may have urushiol on them.

How To Prevent Poison Ivy Rash From Spreading

If you're going outdoors and think you might come into contact with poison ivy, learn how to identify the plant. If you see it while you're out and about, steer clear. You may also want to teach any children you are with how to identify poison ivy as well.

If you know you're going to be in an area that may have poison ivy, you may also want to use an OTC barrier cream as a buffer between urushiol oil and your skin. The active ingredient in these creams is called bentoquatum, which acts as a shield to protect the skin from urushiol.

You can also protect yourself by wearing long pants, long sleeves, gloves, and boots. If you've been in an area where you might have been exposed, wash the clothes you've worn separately in hot water with detergent, recommends the CDC.

When cleaning tools or other objects, use rubbing alcohol or soap and water. And don a pair of disposable gloves while you're cleaning. This will help protect your hands from picking up any urushiol on the items you're cleaning.

If urushiol oil from a plant does get on your skin, it could spread to other parts of your body if you touch the oil with your fingers and then touch another part of your body. If you think you've been exposed recently, rinse your skin with lukewarm soapy water or take a cool shower (not a bath, as that could spread the oil further). Brush vigorously under your nails.

How To Safely Get Rid of Poison Ivy Plants

If there are poison ivy plants in your yard, you can get rid of them yourself or hire a professional to do it for you. If doing it yourself, make sure you can accurately identify the plant first. When you're ready to start the eradication, wear thick gloves, boots, long sleeves, and pants to make sure your skin doesn't come into contact with the plant.

Poison ivy can be pulled out of the ground like a weed, but make sure you get the roots. Some people use an herbicide as well. And bear in mind that you can still get poison ivy rash from dead plants.

Most importantly, never burn poison ivy. Smoke from the burn will contain urushiol oil and is very harmful if inhaled. It can cause a severe allergic reaction that will make breathing difficult. And the smoke can affect anyone in the direct vicinity of the fire and even people who are far downwind, cautions the National Library of Medicine's online service, MedlinePlus.

Once you're done removing poison ivy, or at least done for the day, wash all your clothes and anything that may have come into contact with the poison ivy. And wash yourself—especially your hands—and scrub under your nails even if you've been wearing gloves.

A Quick Reminder

If you've had poison ivy rash once, there is a good chance you won't forget it. The blisters and itchiness can be very uncomfortable. But there are things you can do to prevent getting the urushiol oil 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 that has 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.

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