Poison ivy, poison oak and poison sumac are plants that produce an oil (urushiol) that causes an allergic reaction in susceptible humans. The inflammation is an immune system reaction to the offending agent's contact with the plant, which leads to burning, itching, redness and blisters. The inflammation is a form of contact dermatitis, an allergic reaction to an allergen that comes into direct contact with the skin. It is not contagious although the oil can be transmitted from person to person on clothing and pets. Poison ivy is more prevalent in the eastern part of the country; poison oak is more prevalent in the southeastern part of the country.

The poison ivy eruptions is characterized by streaks of red, itchy bumps and blisters that appear in the area that came into contact with the plant. The rash begins one to two days after exposure and normally resolves in 14 to 21 days.

Treatment for poison ivy, poison oak and poison sumac is designed to relieve the itching and may include oral antihistamines and cortisone creams (either over-the-counter or prescription). These treatments need to be applied before blisters appear or after the blisters have dried up to be effective. In severe cases, oral steroids, such as prednisone, may be prescribed.

The best form of prevention is to recognize and avoid contact with the plants. This can be difficult because these plants tend to grow around other vegetation. These three poison plants can be distinguished by their classic three-leaf formation. To avoid contact with these plants, wear long sleeves and pants when hiking outdoors and keep to the trails. Tuck the ends of your sleeves into gloves and the bottom of your pants into socks so that no area of skin on your arms or legs is exposed. If you think you have come into contact with a poison plant, wash the area of skin with cool water as quickly as possible to help limit the reaction. Also, wash the clothing you were wearing immediately after exposure. Remember to consider pets that may have been exposed as a source of transferring the oil from the plant.