We have three species of plants that secrete an oil which poisons human beings (no other animals) by contact. Most virulent of these is the poison sumac or "poison elder" (Rhus vertiix), which is distinguished from other sumacs by bearing a white fruit like thin clusters of very small grapes, and by its leaf, the edge of which is smooth instead of notched.
The so-called poison ivy (Rhus toxicodendron) is readily told from the harmless Virginia creeper b\ having three leaves, instead of five, and from the wild bean vine by its lack of conspicuous flowers and pods. There are two varieties: one with a smooth-edged leaf, and the other (rarer) with toothed edges. By some it is called poison vine; by others, poison oak. The latter name should be reserved for Rhus diver siloba, which does not grow east of the Rocky Mountains. All three of these plants are really sumacs, notwithstanding that the "ivy" creeps on the ground, or climbs trees, walls, or fences, like a true vine.
When poison ivy is in bloom, the spores of its pollen are blown hither and yon by every breeze, and those minute spores bear some of the poisonous oil that makes the plant an enemy of the human race. That is why people who are particularly susceptible may be poisoned if they go within ten feet of the plant.
The poison is of an acid nature; consequently if one rubs his skin with an alkali (such as baking soda, weak ammonia, soap, or w7ood ashes) before handling the plant, or immediately after doing so, he will be uninjured. Usually one is not aware that he has come in contact with such a plant until the symptoms of poisoning appear. As soon as his skin reddens and begins to itch he should wash in strong soapsuds, and then with alcohol. Generally this will suffice. It he lets the case go until little watery blisters appear between the fingers and inflammation sets in, he must use stronger measures.
The druggist's prescription is: Add powdered sugar of lead (lead acetate) to weak alcohol (50% to 75%) until no more will dissolve; strain, and wrash the affected parts with it several times a day. A camper is not likely to have this remedy at hand. It is a dangerous poison if swallowed.
Common baking soda, so often mentioned in this book, is more likely to be available. Dissolve as much of it in warm water as the water will take up, and apply. A similar solution of boric acid is even better. Afterward rub some resinol or other good ointment over the affected oarts.
I have cured cases of ivy poisoning that were two or three days old, where both eyes were swelled shut and other parts correspondingly affected, with applications of the tincture of grindelia. But what acts as a specific in many instances may do little good in another. Edward Cave recommends "boiling a dime's worth of cardamon seeds (capsules with seeds in them) in a pint of water, for a bad case, and applying the 'tea' thus made as a lotion when cold. The more frequent the application the quicker the remedy." Another cure, that is highly praised by J, S. McGehee, is three parts olive oil and one part carbolic acid. If this does not redden the skin a little, he adds more of the acid, very gradually, testing until it "nips." Two applications, eight or ten hours apart, generally cure. This, of course, would not be safe to use over a large surface.