Summer brings with it scraped knees, sunburned noses, bathing suit tans, and that itchy, miserable rash of poison ivy.
What They Look Like
Poison ivy, oak, and sumac are not look-alikes, but they all belong to the same genus in the plant family and contain an oily substance call urushiol that causes an itchy, blistering rash in sensitive people. The old adage "Leaves of three, let it be" works sometimes, but the appearance of these plants varies too much to count the leaves, and leave it at that.
Poison ivy is found in most of the country. Usually, it is a vine or shrub of branches with three leaves, but can have up to five. Either shiny or dull, the plant produces yellow or green flowers, white berries, and turns a beautiful red in the autumn.
Poison oak is found in the East, generally as a low shrub, and along the West Coast as a tall vine or taller shrub.
Poison sumac is concentrated in the swampy regions of the American Southeast. Its branches can have between seven and 13 leaves.
Blame it on the Sap
The sap containing urushiol is found in every part of these plants—leaves, berries, roots, stems, flowers—and can seep out whenever the plant structure is broken. Though an intact plant does not cause a rash, all it takes is the brush of a leg or even a strong gust of wind to allow the sap to escape. It easily penetrates the skin, causing the reactions within the skin that lead to the rash. Sap that remains on hands or under nails can be spread through itching or touching different parts of the body.
If sap particles are released into the air during a spring burning of old brush, the oil that rains down can produce a scattered rash on passers-by. If inhaled, it can produce an inflammation in the lungs.