Poison Ivy

Is ubiquitous, and remarkably vile. There's a lot of local variation, but some characteristics are well conserved. Probably most notable are the 'three leaves'; the leaves may be of varying shape but there are always three of them. I always read that the leaves are waxy or oily...well, they are, but they sure don't look it; the oil is what sticks to you to cause the rash.

Being ivy, it's a vine. If the vine has tendrils, you are safe, it's not poison ivy. It never has flowers or berries. If the vine has tenacious roots all along it's length, you'll soon have an itchy rash. If the vine is big enough it'll look almost furry.

Diagnosis is easy, the blistered rash is characteristic, and the history of exposure is confirmatory. The rash is usually described as of a 'linear' distribution, but that's a crock. A particularly entertaining means of exposure is from laundry; its certainly not linear in distribution, and also demonstrates that a first order exposure isn't always necessary. Probably the most misery inducing exposure is by Weed Wacking.

The sooner exposed areas can be vigorously washed with strong soap (liquid Tide works well), the better. You'll still probably get a rash, but hopefully not as much. Topical hydrocortisone should be applied early and often; it can actually prevent the rash if started soon enough, like within thirty minutes or so. Oral antihistamines help, but not much. Topical benedryl will result in allergy to benedryl and should be removed from the market. If the victim is stoic enough to tolerate it, very hot water will cause amazingly intense pruritus for the duration of exposure; itching will then be relieved almost completely for a few hours. Sometimes the only effective treatment is a long steroid taper, at least ten days, fourteen is better, however this is best avoided if at all possible. Secondary infection is always a risk, but the hot water treatment minimizes that particular risk.

Here's some pictures; there are vines bigger than your arm back in the woods. Poison oak is a shrub, but otherwise the same. Poison sumac grows only in water, so it's really not something to worry about most of the time.