"Leaves of three - let it be!" aptly describes this woody vine with 2-4" leaflets in groups of three. The center leaf has a longer stem than the other two. Poison ivy clings to tree trunks and other vertical surfaces with hair-like aerial rootlets that grow out of the stem. If a climbing surface isn't available, poison ivy will grow as a free standing shrub. The leaves of poison ivy turn shades of red and purple in fall.
Poison ivy is caused by an allergic reaction (allergic contact dermatitis) to the oily coating that covers of these plants. The resinous coating is called "urushiol". These are called Rhus plants after the old scientific name (it was changed to toxidendron). A person doesn't have to come in direct contact with the leaves, roots, or branches of Rhus plants to get the rash. One can get it from contaminated clothing. Even in winter the leafless stems and vines can cause the familiar skin rash.
No one is born with sensitivity to Poison ivy, but if exposed enough most people become sensitized at some time and remain allergic. A sensitivity can change at any time. There's no way to desensitize people allergic to Rhus plants. Dogs and other animals are not affected by poison ivy, but people can get the rash by petting a dog that's been exposed.
The rash itself is not contagious, and the fluid in the blisters does not spread the rash. Poison ivy dermatitis appears as soon as four hours or as long as 10 days after the exposure, depending on individual sensitivity and the amount exposure. As the rash appears, any sensitivity a person had begins to increase. One starts to react to the slightest traces of a few molecules on the skin. This causes the rash to appear to be spreading, even after treatment has begun.
Poison ivy dermatitis rashes are self-limited; sooner or later they clear up without treatment. Letting nature take its course with mild poison ivy dermatitis is reasonable, but severe rashes need treatment to ease the misery and disability they cause. The very first time this rash is gotten, it lasts longer than a repeat attack, often 3 or 4 weeks.
Cortisone type preparations taken by mouth are dramatically effective in treating Poison ivy dermatitis rash. It's safe to take these drugs for a short period (2-3 weeks). If a person has a peptic ulcer, high blood pressure, or diabetes, cortisone should be taken only under close medical supervision. Improvement of the rash should be prompt and steady. It depends on getting enough cortisone.
Blisters and itching will improve with moist compresses. Make a batch of "Burows solution" by putting 1 or 2 "Dome-Boro" tablets in a pint of water (available from a pharmacist). Apply this to the blistering areas for 20 minutes two or three times daily. Follow the compresses with the prescribed cream if any. Very hot water stops the itch, but is not good for the skin or the rash.
When the swelling has gone down, stop the compresses and apply only the cream. Cream applied before the blisters and swelling go down are not effective alone. One may bathe or shower as usual, but avoid hot water.
Poison Ivy can be partially prevented by application of "Ivy Block" lotion before going in the woods, and washing off an exposed area with "Technu" liquid as soon as exposure is detected. In the woods, rub the Jewelweed plant on exposed skin. The tannins in this plant may bind the resin and prevent the rash. This does no harm, but is only effective within 15 minutes of exposure. Clothing, pets, and tools need to be washed or one may become re-exposed to the resin.
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