| Poison ivy ( Rhus radicans ) is a woody shrub or vine found throughout the United States . Red-tinged leaves grow in groups of three and have smooth, fine-toothed or lobed margins, and small, yellow-green flowers form cream-colored fruit. The allergen, predominantly 3-n-pentadecylcatechol, is found in the resinous sap material uroshiol, which is produced by the leaves, fruit, stem and bark. Therefore, although delayed-hypersensitivity dermatitits induced by contact with poison ivy is usually considered a summer problem in the northeastern United States , it can (and does) occur year-round.
These photographs, which were taken in southeastern Massachusetts , show the changing appearance of the plant during its growth cycle. In mid-May, before the leaves fully emerge, the vine and the cream-colored fruit are visible (Panel A). In July, the red tinge and shiny appearance of the leaves have faded (Panel B). In October, the leaves change color (Panels C and D) and are shed.
Adapted from The New England Journal of Medicine. Vol. 347. July 4, 2002 |
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