This itchy skin reaction comes from touching certain plants. It's caused by an oil, called "urushiol," found in the sap of these plants. Even a tiny bit of this oil causes a skin reaction in most people.
Which plants should you avoid? Be on the lookout for poison ivy and poison oak. Both grow as a shrub or a vine. Their leaves grow in clusters of three. Also watch for poison sumac. It has feather-shaped leaves with red stems. The leaves are arranged in clusters ranging from five to 13. You may also see berries and small white flowers.
When you touch one of these plants, the urushiol in the sap passes through your skin. Symptoms begin soon after contact, usually within 12 to 48 hours. Your skin may be red, warm, swollen and itchy. You may get a rash, and blisters may form. These may break and ooze and form a crust. It can take about three weeks for your skin to heal.
The best way to prevent this reaction is to avoid these plants and anything that may have touched them. If you think you've come into contact with sap from one of these plants, wash your skin as soon as possible with soap and cold water. Creams and ointments can help the itching. If your reaction is severe, your doctor can prescribe a stronger medicine.