Pacific poison-oak, a member of the sumac family,
a deciduous plant that grows throughout many parts of west coast.
Urushiol, found on the stems, berries and leaves is the main component of
the oily resin that
causes rashes and blistering. Poison oak can survive
under a wide range of temperatures, elevations, soil types, moisture
Western poison oak is variable in plant growth and leaf appearance. It can
grow as a dense shrub, a tree with a 3” – 8” trunk or as a climbing vine.
When Pacific poison-oak grows as a shrub, it can reach
up to 13 feet tall. When poison oak grows as a vine or tree, stems can reach
up to 82 feet long. Twigs can be hairless to sparsely hairy and gray to
generally resembling the leaves of a true oak, consist of three, and
sometimes up to five leaflets but three leaflet leaves are most common. Leaf
edges can be smooth, wavy, or have slightly rounded lobes. The upper leaf
surface is hairless, or nearly so, and usually slightly glossy. The lower
surface usually has sparse, short hairs. Leaves turn bright red in the
White flowers form in the spring
leaf axils, where the leaf meets or connects to the stalk, and white
or tan berries usually form later in the summer
Without leaves, poison oak stems may sometimes be
identified by occasional black marks where its milky sap may have oozed and
the map indicates, western poison oak is found only on the Pacific Coast of
the United States and of Canada. southern Canada to the Baja California
Urushiol binds to the skin on contact, where it causes severe itching that
often develops into a red rash or flesh colored bumps and blistering.
Symptoms generally appear 12 to 48 hours later. The rash can be
treated with Calamine lotion or other over the counter remedies such as
oatmeal baths and baking soda. In severe cases hospitalization may be
required or if the plant has been ingested.
Urushiol oil can remain active for several years, so
handling dead leaves or vines can cause a reaction. In addition, oil
transferred from the plant to other objects (such as pet fur) can cause the
rash if it comes into contact with the skin.
Severe respiratory irritation can be induced by
breathing the smoke from burning plant material. Repeated exposure often
results in increased sensitivity.