Poison ivy, poison oak, and poison sumac are plants that produce an oil (urushiol) that causes an allergic reaction among humans. The inflammation is a reaction to contact with any part of 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. Poison ivy is more prevalent in the eastern part of the country; poison oak is more prevalent in the southeastern part of the country.
Poison ivy is characterized by 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. The rash first appears in curved lines and will clear up on its own 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.