Poison Oak Rash Symptoms and Treatment Options, According to Experts

Keep this in mind if you went for a hike and came back with an angry-looking rash.

Poison oak, poison ivy, and poison sumac cause some 50 million allergic rashes each year in the United States, the American Skin Association (ASA) says. That makes them the most common allergic reaction in the country. In fact, most people who brush up against a poisonous plant will have some level of an allergic reaction to it.

According to John's Hopkin's Medicine (JHM), the exact substance to blame for the allergic reaction is urushiol—an oil found on the plant's sap-coated leaves, stem, and other parts. If the oil touches your skin, there's a good chance you will develop a rash within 72 hours. That rash can be very itchy and there may be blisters, so it's important not to itch.

If you spend a lot of time outdoors, you should know how to spot a poison oak plant and what to do if you're exposed to it. This article covers how to identify a poison oak plant, along with what symptoms to look out for if you have an allergic reaction.

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What Does Poison Oak Look Like?

Poison oak is native to most of North America, except for Alaska, Hawaii, and parts of the west coast. It can be found in forests, fields, and wetlands, along roads and streams, and even in urban parks and back yards, says the Centers for Disease Control (CDC).

Many harmless plants look similar to poison oak, which can make identifying it all the more difficult. In the eastern and southern US, poison oak appears as a low-growing shrub, reaching between 3 to 10 feet tall, according to Oregon State University (OSU). In the Pacific United States, poison oak may be a low-growing shrub or a vine that can coil up to 100 feet tall around a tree.

There can be some variation in the plant's color depending on its age and the time of year. While mature poison oak shrubs and vines are light to dark green and fuzzy, immature plants may be bright red to reddish-brown in color. Poison oak loses its plants early in the fall, often before other plants around it. As the leaves die, they can also turn reddish-brown to bright red, says OSU.

You may have heard the expression, "Leaves of three, let it be!" A single poison oak shrub typically has multiple clusters of three leaflets, with each leaflet growing between 1 to 6 inches in length, OSU states. Poison oak plants sometimes sprout white, glossy berries as well.

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Urushiol in Poison Oak Sap

"The [poison oak] plant produces an oil called urushiol that can cause [a] rash in people allergic to it," Debra Jaliman, MD, a board-certified dermatologist and assistant clinical professor of dermatology at the Icahn School of Medicine at Mount Sinai, told Health.

Most people who come in contact with urushiol will start to develop symptoms within a few hours to a few days. But since urushiol is colorless and odorless, many people don't realize they were exposed to it until a rash appears, the ASA says.

In addition to coating poison oak leaves, urushiol is also found on the plant's stem, Joshua Zeichner, MD, associate director of cosmetic and clinical research in dermatology at Mount Sinai Hospital told Health. "When your skin comes in contact with the plant's leaves, the urushiol touches the skin and elicits an immune response."

It's also important to know that you don't have to come into direct contact with poison oak to develop a rash—you can get it from simply touching something else that has come into contact with it. One example of this is if your pet touches poison oak or another urushiol-containing plant, they can spread it to you via their fur, Dr. Jalima said.

Symptoms of a Poison Oak Rash

Generally speaking, the main symptom that comes after exposure to a poison oak plant (or other similar plants) is a red rash within a few days of contact, the CDC says.

"The rash typically comes in streaks because it only develops in the areas [where] the leaves brush up against the skin," said Dr. Zeichner. "[But] if you touch the areas of skin exposed to the urushiol, you can actually spread it to other parts of the body through your fingertips."

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The rashes may also occur in stages. "[First], the rash look like red, itchy bumps on the skin," said Dr. Jaliman. "Then it will become blistered, and then crusted." It can take up to two weeks for a poison oak rash to fully heal, as long as there's no infection, says the ASA.

While most people will only experience a red, itchy rash, a portion of the population may develop a more serious allergic reaction. Around 10%-15% of the US population is severely allergic to urushiol, according to the ASA.

Symptoms of a severe allergic reaction can be life-threatening and you should never try to treat it on your own. If you develop any of the following symptoms, you should seek immediate medical care:

  • Difficulty breathing or swallowing
  • A rash around your eyes, mouth, or on your genitals
  • Facial swelling, especially around your eyes
  • Severe itching that prevents sleep and worsens over time
  • Rashes on most of your body
  • If you develop a fever (in addition to basic poison oak symptoms)

What To Do if You Have Been Exposed to Poison Oak

If you think you've been exposed to poison oak, the first thing you want to do is wash your skin thoroughly with soap and water, said Dr. Jaliman. This helps to prevent spreading the oil to other parts of your body.

To help with itching—which you don't want to do—Dr. Jaliman advised using cool compresses or a short, lukewarm bath with colloidal oatmeal. The experts agreed that using topical ointments like OTC cortisone cream or calamine lotion can reduce itching and inflammation. Anti-histamines like Benadryl can help reduce the allergic reaction, said Dr. Jaliman, while Dr. Zeichner said Vaseline can also help soothe and protect irritated areas.

Oral steroids are sometimes be prescribed for more severe allergic reactions, said Dr. Stevenson. And if the rash is extensive, you should see a dermatologist who can prescribe prescription strength creams or medication. "Prednisone can be taken and will get rid of this rash within a few days to a week," said Dr. Jaliman.

Preventing Poison Oak Exposure

Prevention should be your first line of defense against poison oak rashes. "Know how to identify the plant and avoid it. If you're going to be in a woody area, make sure to wear long pants and sleeves," Dr. Zeichner advised. Dr. Jaliman also recommended ivy blocker products, like Ivy X, which "create a barrier on your skin, making it harder to get the rash."

In addition to protective barriers and layers, Dr. Jaliman suggested washing materials that may have encountered these plants and could bring the oils indoors, such as gardening tools and gloves, the clothes you wore during the outdoor encounter, and even your pets.

Last but not least, always remember to stay aware of your surroundings. Whether you're exploring the outdoors alone, with friends, or with children, make sure to keep your eyes peeled for poison oak and let those in your group know if you see anything suspicious.

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