Ask Mr. Smarty Plants

Great questions! From the www.wildflower.org website, here's some information about this Virginia creeper (Parthenocissus quinquefolia), a native vine ... A woody, deciduous vine, Virginia creeper can be high-climbing or trailing, 3-40 ft.; the structure on which it climbs is the limiting factor. Virginia creeper climbs by means of tendrils with disks that fasten onto bark or rock. Its leaves, with 5 leaflets, occasionally 3 or 7, radiating from the tip of the petiole, coarsely toothed, with a pointed tip, and tapered to the base, up to 6 inches long. Leaves provide early fall color, turning brilliant mauve, red and purple. Inconspicuous flowers small, greenish, in clusters, appearing in spring. Fruit bluish, about 1/4 inch in diameter.

Virginia creeper can be used as a climbing vine or ground cover, its leaves carpeting any surface in luxuriant green before turning brilliant colors in the fall. Its tendrils end in adhesive-like tips, giving this vine the ability to cement itself to walls and therefore need no support. The presence of adhesive tips instead of penetrating rootlets also means it doesn't damage buildings the way some vines do. It is one of the earliest vines to color in the fall. A vigorous grower, it tolerates most soils and climatic conditions.

In years past, children learned a rhyme to help distinguish Virginia Creeper from the somewhat similar-looking and highly toxic Poison Ivy (Toxicodendron radicans): Leaves of three, let it be; Leaves of five, let it thrive. Poison Ivy leaflets are normally in groups of three, while those of Virginia creeper are in groups of five. The berries of Virginia Creeper can be harmful if ingested, however, and the rest of the plant contains raphides, which irritate the skin of some people.

Warning: POISONOUS PARTS: Berries. Highly Toxic, May be Fatal if Eaten! Symptoms include nausea, abdominal pain, bloody vomiting and diarrhea, dilated pupils, headache, sweating, weak pulse, drowsiness, twitching of face. Toxic Principle: Oxalic acid and possibly others. (Poisonous Plants of N.C.) Also, the plants tissues contain raphides, which can irritate the skin of some people. It is far less likely to irritate, and less irritating than, Poison Ivy (Toxicodendron radicans), though, which it somewhat resembles and with which it is often confused.

So, to answer your question, Virginia creeper does cause a rash for some people but not nearly as many people as poison ivy does and not as severe. There are references online that say that Virginia creeper only is a problem with sensitive people. There is no correlation between a rash caused by oxalic acid (also found in uncooked rhubarb, spinach, chard and beet greens) and  and the allergic reaction caused by a peanut allergy. Plants for a Future notes that "The tissues of the plant contain microscopic, irritating needle-like crystals called raphides." And the Regional Poison Control Centre at the University of California, Davis Medical Center has this information about Oxalates: "The juice or sap of these plants contains oxalate crystals. Chewing these
plants may cause pain and irritation of the mouth, lips, and tongue. Swelling of the
throat may cause breathing difficulties."