| Poison ivy, poison oak and poison sumac can all cause dermatitis from the urushiol in their sap. |
| When urushiol comes in contact with the skin, it initiates the contact hypersensitivity reaction. |
| These products often lay a polymer film on the skin that prevents urushiol from permeating to the dermal layer and, in so doing, function as a barrier. |
| Upon exposure to air, urushiol can turn dark brown, which makes it easier to spot. |
| Birds, for example, are unfazed by urushiol, the toxic oil produced by poison ivy, and in fact seem to love the berries produced by the plants. |
| The toxic principle, urushiol, is produced in the resinous juice of the resin ducts of the leaves, flowers, fruits, and bark of stems and roots but not in the pollen grains. |
