PLANT CONTACT DERMATITIS
Contact dermatitis is an inflammation of the skin due to an allergic reaction to a
substance with which it has come into contact. Plant contact dermatitis is a skin
eruption caused by direct or indirect contact with a toxic plant or with direct or indirect
contact with the sap (juice) of a toxic plant. In the United States (US), the most common
plants that cause these skin eruptions are poison ivy (Rhus radicans), poison oak (Rhus
diversiloba), and poison sumac (Rhus vernix). All three of these plants contain urushiol
(pronounced u-roo'-she-ol), a toxic irritant. Urushiol is a clear, gummy, heavy oil
contained inside all parts of the plant (leaves, stems, and roots). When the plant is
damaged, the urushiol comes to the surface. If urushiol comes into contact with skin, it
penetrates the outer layer of skin and binds itself to skin cells. The body then reacts to
the toxic substance.
a. The urushiol does not have to pass directly from plant to skin. The urushiol
can stick to boots, clothing, weapons, or animal fur with which it comes into contact.
When a person touches the object (minutes, days, or months later), the urushiol attacks
his skin. Even the smoke from burning plants containing urushiol carries droplets of
urushiol which can get on a person's skin. If the smoke containing urushiol is inhaled,
the urushiol can affect the person's respiratory system and create breathing problems.
Urushiol can remain active even if the plant has died and dried.
b. In the US, about 25 percent of the people are immune to urushiol,
about 25 percent are mildly sensitive, about 30 percent are moderately sensitive, and
about 20 percent are extremely sensitive to urushiol.
IDENTIFY POISON IVY, POISON OAK, AND POISON SUMAC
a. Poison Ivy. Poison ivy (figure 3-1) is also known as three-leaf ivy, poison
creeper, climbing sumac, oak leaf ivy, and mercury.
Poison ivy grows as a small plant, either as a vine or shrub.
Leaves of the poison ivy plant always consist of three glossy, pointed
Poison ivy has greenish-white flowers and berries that grow in clusters.