What is Poison Ivy?

Poison Ivy, Oak and Sumac are plants known to cause itchy rashes with blisters or bumps in most people and occasionally life-threatening reactions in severe cases.


What causes Poison Ivy?

The rash is most commonly caused by direct contact with an oil in these plants caused urushiol. About 85% of people are sensitive to this oil, which is present in all parts of the plant, including leaves, stems and roots. Most people will develop itching and a rash within 12 to 72 hours after initial contact with the plant oil. The rash itself is not contagious to other people, only contact with the oil itself will cause symptoms, although the rash can sometimes appear to spread due to a delayed reaction or additional contact with .

Indirect contact happens when you touch something with urushiol on it, such as clothing, a gardening implement, sporting equipment or even a pet. Fortunately, only humans are susceptible to rashes from urushiol, and only if they touch the oil directly. It is not possible to get a rash from touching someone else’s rash.

Airborne contact happens when poison ivy, poison oak or poison sumac is burned and small amounts of urushiol are released in the air. These small particles can land on the skin.

What are the symptoms of poison ivy?

In typical mild cases, contact with the oil causes a reddish rash or red streaks and severe itching. Raised bumps resembling hives and blistering are also common. Slight swelling is also typical, but severe swelling in the face or eyes swelling shut is a sign of a serious reaction which requires immediate medical treatment. As the rash heals, crusty skin from the burst blisters may develop.

You should go to an emergency room if you have symptoms of a severe reaction, such as difficulty breathing, swallowing or severe swelling, especially in the face. A serious reaction is more likely if the rash covers a large area of the body, the rash develops on the face or genitals, or there are large blisters. Difficulty sleeping due to excessive itching or discomfort are also signs that require medical attention.

How is it diagnosed and treated?

At Dermatology of Seattle, we can determine whether your rash is due to poison ivy, oak, or sumac or another condition.

In mild cases, the rash will go away within about 1-3 weeks. If you know for certain that your rash was caused by contact with one of these plants, you can treat it yourself at home. First, rinse off any excess oil using warm water and wash clothing and other items that may have come into contact with the plant, including pets. To treat the itching, dermatologists frequently recommend using remedies such as an oatmeal bath or calamine lotion. Antihistamine pills can also sometimes help, but avoid applying antihistamine directly to the rash, as that can actually make it worse.

A serious reaction may need prescription medication to treat, such as a steroid ointment or prednisone in particularly severe reactions. Antibiotics may also be needed if you develop symptoms of infection, such as a fever, or pain and swelling around the rash.