Poison Oak

Medically Reviewed By William C. Lloyd III, MD, FACS
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What is poison oak?

Poison oak is a common plant that grows in all U.S. states but is most commonly found in the western part of the United States. Poison oak plants typically contain three leaves with yellow or green flowers. When your skin comes in contact with poison oak you can develop an allergic dermatitis rash in reaction to urushiol, the oil found in the poison oak plant. A rash can also occur when skin comes in contact with gardening tools, clothes, or a pet’s fur that has come in contact with poison oak.

About 80 to 90% of people who come in contact with poison oak oil will develop a rash. Only a small amount of urushiol is needed to cause a rash, about the size of a grain of table salt. The rash appears on the outer layer of skin and may look like small red, swollen, itchy bumps or black spots. Outdoor workers or people participating in frequent outdoor activities are at increased risk of exposure to poison oak.

Poison oak rash can take time to develop after initial exposure to the plant. The rash typically develops within a few hours of exposure in people with previous exposure to poison oak and 2 to 3 weeks in people who have never had a poison oak rash. Treatment includes over-the-counter topical products for symptom management or, in severe cases, prescription medication.

Severe reactions can occur in those who have previously had a severe reaction to poison oak or in people who have inhaled smoke from burning poison oak. If left untreated, inhalation can lead to difficulty breathing or severe, anaphylactic reaction in those who have a known severe reaction to contact with poison oak. Seek medical care immediately (call 911) if you have a life-threatening reaction to poison oak, including difficulty breathing, chest tightness, rapid heart rate, drooling, or swelling in the lips, mouth or throat.

What are the symptoms of poison oak?

Exposure to poison oak typically causes a mild to moderate rash on the outer layer of skin depending on the extent of exposure.

Common symptoms of poison oak

The most common symptoms of poison oak include:

  • Red, itchy bumps

  • Blisters

  • Swelling

  • Black spots on skin

Serious symptoms that might indicate a life-threatening condition

In some cases, poison oak rash can be life-threatening. Seek immediate medical care (call 911) if someone has any of these life-threatening symptoms including:

  • Fever higher than 100°F  

  • Difficulty breathing

  • Swelling around the eyes, mouth, or genitals

What does poison oak look like?

Poison oak is the common term for the Toxicodendron diversilobum plant, also known as western poison oak or Pacific poison oak. Many people react to urushiol, an oil present on the surface of the plant's leaves and stems.

Poison Oak Plant
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Contact with urushiol can cause an allergic reaction, with symptoms including rash, itchy skin, and swelling.

Poison Oak Rash On Skin Close Up
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What causes poison oak?

Poison oak rash is caused by the skin coming in contact with the poison oak plant directly or an object or pet contaminated by urushiol, the oil produced by the poison oak plant. Your skin absorbs the oil from poison oak quickly, so there is only a short amount of time the rash can spread to other areas of your skin. Touching the rash will not spread it to other areas of the body and the rash is not contagious. Poison ivy and poison sumac are in the same Toxicodendron family of plants and cause a similar type of rash as poison oak.

What are the risk factors for poison oak?

Risk of a poison oak rash increases with outdoor activities that place you at higher likelihood of exposure to poison oak including:

  • Gardening

  • Hiking

  • Roofing

  • Firefighting

  • Landscaping

  • Farming

Reducing your risk of poison oak

You may be able to lower your risk of poison oak by:

  • Covering up with long sleeve clothing, pants, soak, boots, and gloves

  • Applying non-prescription ivy blocker or barrier cream to the skin

  • Removing or applying herbicide to poison oak plants in your yard or garden

  • Washing contaminated objects or pet fur

Discussing your risk factors with your primary care doctor for poison oak can help reduce your risk of rash and help you determine appropriate preventative measures to take if you are an outdoor worker or frequently exposed to poison oak.

How do doctors diagnose poison oak?

Your doctor will be able to diagnose poison oak rash with a visual exam. Your doctor may also ask you several questions related to poison oak including:

  • How long have you had the rash?

  • Did you come in contact with any poisonous plants or other points of contamination?

  • What symptoms are you experiencing from the rash?

  • Does anything help relieve your symptoms?

What are the treatments for poison oak?

Treatment of poison oak rash aims to reduce redness and itching. Rashes usually go away within 1 to 2 weeks and can be relieved with the following treatments:

  • Anti-itch creams such as calamine lotion or hydrocortisone creams

  • Oral antihistamines such as Benadryl

Home remedies for poison oak

At home, you can use colloidal oatmeal baths such as Aveeno and cold compresses to help reduce redness, swelling, and itching.

Immediately wash your skin, clothes, and contaminated objects with warm, soapy water if you have come in contact with poison oak.

What are the potential complications of poison oak?

In severe reactions, or if left untreated, poison oak can result in complications including:

  • Infection or bleeding from scratching the skin

  • Irritation to the nasal passages or lungs from inhaling smoke from burning poison oak

  • Signs of anaphylaxis such as difficulty breathing, widespread hives, and severe swelling

What are some conditions related to poison oak?

Poison ivy and poison sumac are two other plants that contain urushiol, the oily resin that causes a rash similar to poison oak. Edible cousins that harbor urushiol include pistachios, the skin of mangos, and the shells of cashews. They can cause a similar rash involving the fingers and mouth. The symptoms and treatment for poison ivy and poison sumac are the same as poison oak. Contact your doctor or healthcare provider if you have had possible exposure to poison ivy or poison sumac.

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2021 Jul 19
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THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
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  4. Poison Ivy, Oak, and Sumac. American Academy of Dermatology Association. https://www.aad.org/public/everyday-care/itchy-skin/poison-ivy
  5. Poisonous Plants. Centers for Disease Control and Prevention. https://www.cdc.gov/niosh/topics/plants/default.html