The weeping, itchy rash caused by these plants is the most common allergic contact dermatitis in North America, and an estimated 10 to 50 million Americans suffer from it every year.
Identifying poison oak is the best way to avoid it! In open areas with full sunlight, poison oak forms a dense, leafy shrub usually 1 to 6 feet high. In shaded areas, it grows as a climbing vine, up to 75 feet or more, supporting itself on other vegetation or upright objects. In my case, it is entangled in the hedges which is how I came in contact with it while trimming them.
Poison oak is not a true oak, but its leaves are superficially similar to a true oak, grow singly, not in groups. The adage ‘‘leaves of three, let them be’’ refers to each leaf of poison oak having three leaflets. This adage is not always true though. Leaves normally consist of three leaflets with the stalk of the central leaflet being longer than those of the other two. It's uncommon, but leaves can have five or seven leaflets and in even more rare cases nine.
Each leaflet is 1 to 4 inches long with toothed edges. The leaves' surface ranges from glossy to dull in color, thin to leathery in texture and sometimes even "hairy."
Poison oak is deciduous, meaning that that seasonally it sheds its leaves. This can make detection and identification almost impossible in the winter and early spring because the plant has no leaves.
In early spring new leaves are green or sometimes light red and they grow to the left then to the right along the stem. Poison oak produces small, white-green flowers at the point where leaves attach to the stem. It also produces whitish-green, round fruit in late summer and can persist into fall and winter.
Poison oak is a long lived. The seeds have a hard coat and can remain viable in the soil for years. Once they germinate and the plants become established, plants can form suckers, or underground stems, and spread. In addition, vines that contact the ground often form roots, creating new plants and over time a single plant can cover a huge area.
Believe it or not, the leaves and stems are a food source for many animals including deer and livestock. Birds and other animals eat the berries without adverse effects. The passage of the hard seeds through the digestive tract facilitates germination by reducing the period of dormancy.
Poison oak, poison ivy, and poison sumac causes allergic contact dermatitis in humans. The plant oil (urushiol) does not appear to cause allergic reactions in cats or dogs because their coats protect them from the oil unless the plant cpomes in comtact with an area that has no hair.
Approximately 50-75 percent of the adult population is sensitive to the plant's oil. Peak sensitization occurs between 8 and 14 years of age. Once a reaction occurs, repeated exposures further increase sensitivity. Conversely, long periods with no exposure will reduce an individual’s susceptibility. There is also evidence that suggests children born to two sensitive parents will also be sensitive.
Contrary to popular belief, just coming in contact with poison oak doesn’t mean an individual will get a rash. The oil is found in the stems, roots, leaves and skin of the fruits so usually damage is required for plants to release the oil. For this reason slight contact with uninjured leaves will not result in getting a rash.
Urushiol is dries quickly and can persist on objects and retain its ability to cause an allergic response for months or even years. This means that tools, clothing, pets, vehicles, and other objects that come in contact with the oil can continue to spread the oil. When poison oak is burned, the oils can disperse via the smoke particles. Breathing this smoke can cause severe respiratory irritation.
In the fall, leaves become enriched with oil which can result in higher levels of exposure. In winter the leaves become dry and fall off and the oils are reabsorbed into the stems making the leaves non-allergenic. Bare stems in the winter, especially if they are damaged, can release oil resulting in exposure.
There is currently treatment for the rash other than avoiding exposure by covering the skin and washing with soap and water soon after exposure.
Hypo-sensitization medication used to be available, but were taken off the market when they were found ineffective. To date no measures have been found that prevent or act as a cure.
If one is sensitive to poison oak, the skin rapidly absorbs the allergen so the key in minimizing or preventing an outbreak is to remove the oil from your skin as quickly as possible.
The oil degrades in water, but significant amounts can be removed only if washed off immediately. After 10 minutes only about half of th eoil is removed and after 30 minutes it's too late...all of the oil has been absorbed.
Removing the oil is similar to removing grease! The best way to remove it is to wash with a damp washcloth and liquid dishwashing soap going in one direction. Use repetitive, high-pressure, single-direction strokes with the washcloth under warm, running water. This uses friction and heat to remove the glutinous oil.
Research has shown that isopropyl (rubbing) alcohol poured over an exposed area then washed with plenty of cold water is also effective.
Be sure to thoroughly wash your hands, especially under the fingernails. All exposed clothing, equipment and pets should be washed thoroughly in soap and water. Note: using only a small amount of water or disposable hand wipes is more likely to spread the oil than remove it.
Over-the-counter products (Tecnu, Zanfel and special soaps) have also been shown to be effective at removing urushiol oil from the skin.
Once exposed, within 1 to 6 days after exposure, skin irritation and itching will be followed by water blisters, which can exude serum. The serum does not does not transmit the rash to other regions of the body or to other individuals.
Time to appearance and severity of rash depend on the amount of oil absorbed and the skin thickness. The most common culprit for re-exposure are fingernails, clothing, tools, and pets.
The rash, blisters, and itch normally disappear within 1 to 2 weeks without any treatment.
Relieve the itch by using wet compresses or soaking in cool water, applying over-the-counter topical corticosteroid preparations, calamine lotion can help.
See a doctor in the event of a fever, pus, soft yellow scabs or tenderness of the rash occurs. Or, if the itching gets worse or keeps you awake at night, the rash spreads to your eyes, mouth, genital area, or covers more than one-fourth of your skin. See a doctor if the rash does not improve within a few weeks, is widespread and severe or you have difficulty breathing.
Physically removing poison oak by pulling it by hand or using a shovel is possible, but it is essential to remove the entire plant including its roots.
The plants should be removed in early spring or late fall when the soil is moist and it is easier to dislodge roots. Using a shovel when the soil is dry will usually just break off the stems, leaving the roots to resprout.
Even the cut and dried brush can cause am outbreak, so bury it, put it in an out-of-the-way location or take it to a disposal site.
When hand pulling poison oak wear appropriate protective clothing, including washable cotton gloves over plastic gloves. Wash equipment, tools and all clothing, including shoes.
There are herbicides available for controlling poison oak and some lawn companies may have the resources to deal with it.
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