Posted on 09/25/2005 10:07:52 AM PDT by yankeedame
Poison ivy is a red, itchy rash caused by the plant that bears its name. Many people get it when they are hiking or working in their garden and accidentally come into direct contact with the plant's leaves, roots, or stems. The poison ivy rash often looks like red lines, and sometimes it forms blisters.
The culprit behind the rash is a chemical in the sap of poison ivy plants called urushiol (oo-roo-shee-ohl). Its name comes from the Japanese word "urushi," meaning lacquer. Urushiol is the same substance that triggers an allergic reaction when people touch poison oak and poison sumac plants. Poison ivy (Toxicodendron radican), Eastern poison oak (Toxicodendron quercifolium), Western poison oak (Toxicodendron diversilobum), and poison sumac (Toxicodendron vernix) are all members of the same family -- Anacardiaceae.
Photo courtesy Jon Sachs, poison-ivy.org
A blistered poison ivy rash
About 85 percent of people are allergic to the urushiol in poison ivy...Only a tiny amount of this chemical -- 1 billionth of a gram -- is enough to cause a rash in many people.
Some people may boast that they've been exposed to poison ivy many times and have never gotten the rash, but that doesn't necessarily mean they're not allergic. Sometimes the allergy doesn't emerge until you've been exposed several times, and some people develop a rash after their very first exposure. It may take up to ten days for the rash to emerge the first time.
The body's immune system is normally in the business of protecting us from bacteria, viruses, and other foreign invaders...But when urushiol from the poison ivy plant touches the skin, it instigates an immune response, called dermatitis, to what would otherwise be a harmless substance. Hay fever is another example of this type of response; in the case of hay fever, the immune system overreacts to pollen, or another plant-produced substance.
Here's how the poison ivy response occurs. Urushiol makes its way down through the skin, where it is metabolized, or broken down. Immune cells called T lymphocytes (or T-cells) recognize the urushiol derivatives as a foreign substance, or antigen.
They send out inflammatory signals called cytokines, which bring in white blood cells. Under orders from the cytokines, these white blood cells turn into macrophages. The macrophages eat foreign substances, but in doing so they also damage normal tissue, resulting in the skin inflammation that occurs with poison ivy.
The allergic reaction to poison ivy is known as delayed hypersensitivity. Unlike immediate hypersensitivity, which causes an allergic reaction within minutes of exposure to an antigen, delayed hypersensitivity reactions don't emerge for several hours or even days after the exposure.
Myth: Poison ivy is contagious.
Reality: You can't spread poison ivy by coming into contact with a person who has it, unless that person has urushiol on their skin. You can, however, pick it up by touching a dog that has gotten poison ivy on its fur, or by touching the blade of a weed whacker that you just used to cut down the plants.
Myth: You can spread poison ivy to other parts of your body by picking at the blisters on your skin. Reality: The only way you can get poison ivy is by touching the plant, or by touching an object that has come into direct contact with the plant and has urushiol on it. If you scratch or pick at the rash and blisters, you may cause an infection, but you won't cause the rash to spread. Although the rash may appear to "spread," it is only because the reaction occurs more slowly on some parts of the body than it does in other parts.
Myth: If I eat poison ivy, I'll become immune to it in the future.
Reality: This is not only untrue, but it can be lethal. Eating poison ivy can cause a potentially fatal allergic reaction. Some animals, including deer, happily eat poison ivy with no ill effects.
Myth: Some people are so sensitive to poison ivy that they can catch it just by being near the plant.
Reality: You have to touch the plant to get poison ivy - just being close to it will not get urushiol on your skin.
Myth: You can't get poison ivy from a dead plant.
Reality: Urushiol can linger on surfaces -- including the poison ivy plant -- for several years, even after the plant has died.
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Remember: The leaves of the poison ivy plant turn red and yellow for fall.
She comes on like a rose
And everybody knows
She'll get you in dutch
Well you can look but you'd better not touch
Poison Ivy, Poison Ivy
Well late at night when you're sleepin'
Poison Ivy comes a creepin' all around
She's pretty as a daisy
But look out man she's crazy
She'll really do you in
If you let her get under your skin
Poison Ivy, Poison Ivy
Well late at night when you're sleepin
Poison Ivy comes a creepin' all around
Measles make mumpy
Mumps'll make you lumpy
Chicken pox will make you jump and twitch
Common cold'll cool you
Whooping cough will fool you
But Poison Ivy Lord will make you itch
You're gonna need an ocean ah
Of Calamine lotion ah
You'll be scratching like a hound
The minute you start to mess around
Poison Ivy, Poison Ivy
Well late at night when you're sleepin'
Poison Ivy comes a creepin' all around
(Lieber/Stoller)
"Some people may boast that they've been exposed to poison ivy many times and have never gotten the rash, but that doesn't necessarily mean they're not allergic."
And, for some folks that's true. The only time I ever got a rash was when I had some cuts on my legs. Even then, it was very mild.
True Japanese Laquer, which is aplied in hundreds or thousands of thin coats and is more durable than epoxy, is made from the sap of another member of the sumac family that rarely causes a reaction. Hence the name.
So9
Ping
"Myth: Some people are so sensitive to poison ivy that they can catch it just by being near the plant.
Reality: You have to touch the plant to get poison ivy - just being close to it will not get urushiol on your skin. "
You can also get it airborne. Burning leaves ot trash that have poison ivy in it, will get the oils airborne and if they settle on someone sensitive to it, they will break out.
And if they inhale it...
thanks.
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