Health Conditions A-Z Skin, Hair & Nail Conditions 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. By Madison Yauger Updated on November 28, 2022 Medically reviewed by Farah Khan, MD Medically reviewed by Farah Khan, MD Farah Khan, MD, is an allergist/immunologist that treats pediatric and adult patients in her private practice in Northern Virginia. learn more Share this page on Facebook Share this page on Twitter Share this page on Pinterest Email this page Poison oak, poison ivy, and poison sumac cause some 50 million allergic rashes each year in the United States. 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. 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. 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. Find out how to identify a poison oak plant, along with what symptoms to look out for if you have an allergic reaction. AdobeStock What Poison Oak Looks 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 backyards, according to the Centers for Disease Control (CDC). Many harmless plants look similar to poison oak, which can make identifying it all the more difficult. Poison oak appears as a shrub and the leaves look similar to poison ivy. There can be some variation in the plant's color depending on its age and the time of year. While most of the time poison oak shrubs are green and fuzzy, in the fall the plants may be bright red and yellow in color. You may have heard the expression, "Leaves of three, let it be!" A single poison oak shrub typically has multiple clusters of three leaflets. Poison oak plants sometimes sprout white, glossy berries as well. AdobeStock Urushiol in Poison Oak Sap "The [poison oak] plant produces an oil called urushiol that can cause [a] rash in people allergic to it," said Debra Jaliman, MD, a board-certified dermatologist and assistant clinical professor of dermatology at the Icahn School of Medicine at Mount Sinai. 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. In addition to coating poison oak leaves, urushiol is also found on the plant's stem, said Joshua Zeichner, MD, associate director of cosmetic and clinical research in dermatology at Mount Sinai Hospital. "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. If you burn poison oak leaves—like if they're used as kindling for a fire—that can cause urushiol to be released in the form of smoke which can be inhaled and cause severe breathing issues. 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 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." DermNet NZ 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. 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. 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 the spreading of 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. Antihistamines 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 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. What Is Poison Ivy? A Quick Review Poison oak can cause an annoying, itchy rash. As long as you know what a poison oak plant looks like, you can prevent yourself becoming exposed to the urushiol oil that causes this rash. If you do come into contact with poison oak, you can apply cool compresses or soak in an oatmeal bath to soothe the itching. Otherwise, the rash will go away after a couple of weeks. If you notice any symptoms of an allergic reaction, notify a healthcare professional right away. Was this page helpful? Thanks for your feedback! Tell us why! Other Submit 4 Sources Health.com uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. American Skin Association. Poison ivy, sumac and oak. Centers for Disease Control and Prevention. Poisonous plants: geographic distribution. National Capital Poison Center. Poison ivy, poison oak, and poison sumac. American Academy of Dermatology. Poison ivy, oak, and sumac: how to treat the rash.