Everything you need to know: Poison ivy, poison oak, poison sumac
Everything you need to know: Poison ivy, poison oak, poison sumac
by Alex Reshanov in Blogs » Earth, Science Wire
Toxic Avengers
Aside from being flowering plants, members of the toxic trio bear little relation to their benign namesakes.* But they are related to each other. All three belong to the same genus – Toxicodendron – and share the same itch-producing component – an oil called urushiol. It’s a fierce skin irritant. According to the Centers for Disease Control, between 80 and 90% of the U.S. population exhibits an allergic reaction to urushiol, and at doses as low as 50 micrograms (less than a grain of salt).
Urushiol is found it all parts of the plant (leaves, stems, even berries). It seeps from any damaged portion and stays active for, ugh, one to five years. While the leaves generally bloom from spring to fall, even the dead and withered remains of the plants can be sufficiently coated in urushiol to cause bouts of wintertime itching.
Toxicodendrons are native to North America, with most U.S. states (and several Canadian provinces) being home to at least one, if not all, of the dreaded poisoners. They’re frustratingly varied in appearance. Poison oak and poison ivy usually (but, sigh, not always) exhibit the infamous “leaves of three” configuration, but poison sumac sports anywhere from seven to thirteen leaves. Leaves vary in color depending on the season, and growth patterns can be different even within the same species. Sometimes they’re shrubs, other times vines. Master of disguise poison ivy (Toxicodendron radicans) can be a shrub, a trailing vine, or a climbing vine. Good luck staying out of its path.
Poison sumac (Toxicodendron vernix) is considered the most potent of the three, but luckily it doesn’t have the widest distribution. That honor goes to the frighteningly ubiquitous poison ivy. Poison sumac also grows in areas that are less fun to hang out in – swamps and bogs and the like. (Though it would be an especially insult-to-injury-adding experience to have to wade through a bog only to discover you’d acquired a case of poison sumac in the process.)
Look what the cat dragged in…
And if picking up allergic contact dermatitis (medical lingo for miserable plant rash) directly from the source weren’t enough to worry about, you can also get it from your outdoor-loving pets. Cats and dogs don’t seem terribly affected by urushiol, and they’re more than happy to carry it home to you on their furry little backs (and heads, and paws… what a mess). As with anything else that comes into contact with vicious Toxicodendrons, your pet will require thorough washing.
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Family Tree
There’s another urushiol-harboring plant in the Anacardiaceae family that might be of interest to you: the cashew. Yes, delicious snack-tastic cashews were once scary, toxin-coated itch bags. The nut (well, drupe technically) is housed in a double shell, and it is in the shell itself that urushiol is found. When cashews are processed, their shells are removed and any lingering poison is carefully cooked from the nut (even “raw” cashews are steamed before they hit the market.) This explains why cashews are so under-represented in bowls of unshelled nuts waiting to be opened with a festive nutcracker. Cracking a walnut is one thing, but unleashing cashews requires protective clothing.
Shades of red
Some individuals are more profoundly allergic to urushiol than other, and the degree of reaction can change over time. The rash and blistering caused by the toxic oil is slowest to develop after the first exposure. During subsequent interactions with itchy
A number of people seem keen on the idea of building up a tolerance to urushiol so that they can march through poisonous flora with impunity. This isn’t complete insanity. Dermatological experiments on humans have demonstrated some success with this kind of desensitization, though the benefits weren’t always long lasting. ...
First Aid
Contrary to popular belief, poison ivy/oak/sumac isn’t contagious, nor does it spread to other parts of your body (though it may seem like it does because the rash takes time to fully materialize). The only way it can be transmitted is through contact with the oil itself, so if you find yourself afflicted with the rash it’s important to track down every last trace of urushiol.
DO: Wash your skin thoroughly ...
DO: Wash everything else that may have touched the poisonous plants. ...
DON’T: Attempt to destroy the offending plants or any contaminated items with fire. ...
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If you’re especially fed up with these sadistic plants, you can also try moving to Alaska or Hawaii, both of which are Toxicodendron-free. ...
* Poison sumac is the exception, non-itching varieties of sumac are in the same family as the itchy plants (Anacardiaceae.) But poison sumac is the oddball of the three in several ways.
More
http://earthsky.org/earth/lifeform-of-the-week-poison-ivy-poison-oak-poison-sumac?utm_source=EarthSky+News&utm_campaign=993468cf60-EarthSky_News&utm_medium=email&utm_term=0_c643945d79-993468cf60-393525109
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