40 Fun Facts About Poison Ivy

Which nut is rarely sold in its shell, which holds an irritant related to poison ivy's oil?

Cashew shells hold anacardic acid, a skin irritant chemically related to poison ivy's oil, which is why the nuts are shelled and then roasted or steamed before anyone eats them.

Which actress played the Batman villain Poison Ivy in the 1997 film Batman & Robin?

Uma Thurman played the villain, whose comic-book alter ego Pamela Isley is a doctor of botany turned eco-terrorist with the power to command plant life.

Which way of getting rid of poison ivy is most dangerous, sending its irritant oil into the lungs?

Burning it releases droplets of the oil into the smoke, which can inflame the eyes, throat and lungs of anyone downwind who breathes it in.

Which colonist published the first written account of poison ivy, likening it to English ivy?

John Smith described the plant in 1624, noting that a touch brought redness, itching and blisters, yet he argued it had earned its bad name unfairly because the blisters soon passed.

Which major US city grew up on the site of a Tongva village whose name meant 'poison oak place'?

Los Angeles grew over the old village of Yaanga, and finds linked to it turned up when Union Station was built; poison oak is a close cousin of poison ivy with the same irritant oil.

Rising levels of which gas make poison ivy grow faster and turn its irritant oil more potent?

Carbon dioxide feeds the vine: in a six-year forest experiment, poison ivy given extra of the gas photosynthesised more, grew bigger and made a more allergenic form of the oil behind the rash.

Which tropical fruit's skin and sap can give people who react to poison ivy a very similar rash?

Mango trees sit in the same plant family as poison ivy, and their sap, leaves and fruit skin are the most common cause of plant rashes in Hawaii during the ripening season.

Which farm animals are often put to work clearing poison ivy because they will browse on the plant?

Goats eat poison ivy without trouble, and their browsing can partly control the plant, though it often grows back once the animals are moved on.

A few daring horticulturists in Japan and the United States grow poison ivy as which art form?

Bonsai growers prize poison ivy for its thick woody trunk, shiny green leaves and brilliant autumn colour, and train it as carefully as any maple or juniper.

What colour are the ripe berries of poison ivy, which many birds eat through the winter?

White or greyish berries ripen from August, and the seeds stay viable after passing through a bird, which helps poison ivy reach new ground.

What produces the fluid in poison ivy blisters, which many wrongly blame for spreading the rash?

The person's own body makes the fluid as blood vessels leak beneath the inflamed skin, so it holds none of the plant's oil and cannot pass the rash on.

The irritant oil in poison ivy is named after the Japanese word for which glossy craft finish?

Lacquer for traditional bowls and boxes is refined from the sap of a tree in poison ivy's own genus, and the raw sap gives newcomers to the workshop the same itchy rash.

Which French consort, an avid amateur botanist, grew poison ivy in her gardens as a curiosity?

Joséphine Bonaparte had poison ivy and poison sumac flourishing near Paris by 1804, and the flower painter Redouté drew the ivy with its berries for a luxury book on trees and shrubs.

A French doctor's letter about his poison ivy plants got him arrested for plotting with which power?

The Russians were suspected because he had asked after his dear Rhus, the plant's old Latin name, which sounded like the French word for those enemy troops; he narrowly escaped the guillotine.

Which climbing vine, with five leaflets on most of its leaves, is often mistaken for poison ivy?

Virginia creeper often shares a tree with poison ivy, and its sap holds needle-shaped oxalate crystals that can irritate sensitive skin in their own right.

How can a pet dog give its owner a poison ivy rash without showing any reaction of its own?

Carrying oil on its fur is the risk: most pets are not sensitive to poison ivy, but the oil clings to their coat and rubs off on whoever strokes them.

Which lotion, made from zinc oxide and a little iron oxide, is a classic remedy for poison ivy itch?

Calamine gets its pink tint from the iron oxide, and it sits on the World Health Organization's List of Essential Medicines as a treatment for mild itching.

Which grain product, finely ground into a warm bath, do dermatologists suggest for poison ivy itch?

Oatmeal in its colloidal form is sold at most drugstores for exactly this, and US regulators class it as a skin protectant that relieves minor irritation and itching.

Which American vocal group scored a 1959 Top Ten hit with the Leiber and Stoller song Poison Ivy?

The Coasters reached number 7 on the Billboard Hot 100, and a 1964 cover by Billy Thorpe and the Aztecs kept the Beatles off the top of the Sydney charts during their only Australian tour.

What is the name of the oily compound in poison ivy sap that triggers the itchy rash in most people?

Urushiol is so persistent that it can stay active for several years, which is why handling dead vines, old tools or unwashed clothing can still bring on a rash.

What structures fasten a climbing poison ivy vine to a tree trunk and give it a hairy look?

Aerial rootlets sprout wherever the vine touches bark, so an old one looks like a furry rope running straight up the trunk instead of twining around it.

Wild raspberry canes can resemble poison ivy, but they bear which feature that poison ivy never has?

Thorns settle it: raspberry and bramble canes are prickly and often green, while a poison ivy vine is smooth, brown and woody.

Which maple is often mistaken for poison ivy when it is a young sapling?

Box elder saplings often show three ragged leaflets, but they sit in opposite pairs along the twig, while poison ivy's leaves alternate from side to side.

Which invasive vine of the American South has three leaflets like poison ivy, only larger and hairy?

Kudzu is harmless and even edible, yet it scrambles over other plants and high into trees; its leaflets are bigger than poison ivy's and fuzzy underneath.

Poison sumac, a relative of poison ivy with a stronger punch, grows almost only in which habitat?

Swamps and peat bogs are its home, which spares most hikers: poison sumac is rated more toxic than poison ivy but needs wet soil to grow.

Besides North America, poison ivy is native to which other region of the world?

East Asia has its own species, found in Japan, Korea and Taiwan, which looks so like the American plant that some botanists treat it as a mere variety.

Which wildflower, also called spotted touch-me-not, is a folk remedy for poison ivy rash?

Jewelweed juice is a Native American remedy for itchy rashes, though trials of whether it really works on poison ivy have given conflicting results.

Which class of drugs, including prednisone, do doctors prescribe for severe poison ivy rashes?

Corticosteroids damp down the overactive immune response behind the rash, and a course of prednisone has to be tapered off slowly, never stopped all at once.

Where on the hands can poison ivy oil stay trapped and travel to fresh patches of skin?

Under the fingernails is where the oil lingers, one reason a rash can seem to creep across the skin for days even though scratching the blisters cannot move it.

Sap leaking from a damaged poison ivy plant turns what colour after exposure to the air?

Black is what the sap becomes: it oozes from an injured plant and sets into a dark, tough film as it meets oxygen.

Which 'living fossil' tree, unrelated to poison ivy, has fleshy seeds that can raise a similar rash?

Ginkgo seeds wear a soft, foul-smelling outer coat, and some people who handle it break out in blisters much like those from poison ivy.

Poison ivy and its relatives have been blamed for about a tenth of lost-time injuries at which US federal agency?

The US Forest Service sends crews into the woods and to wildfires, where firefighters often get rashes and inflamed eyes from smoke that carries the oil.

Where does poison ivy grow most thickly, a habit that helps it as suburbs carve up the woods?

Woodland edges give it both sunlight and trees to climb, and building beside wild land keeps creating new margins where poison ivy forms vast, lush colonies.

What is the medical name for the kind of itchy, blistering skin reaction that poison ivy causes?

Contact dermatitis from poison ivy is a delayed allergic response: once sensitised, most people break out two or three days after brushing against the plant.

Botanically, the berry-like fruit of poison ivy is which fruit type, like a cherry or an olive?

Drupe is the botanist's term for a fleshy fruit around a single hard stone; poison ivy's are waxy, about a quarter-inch across and can cling to the vine all winter.

Which immune defenders, activated in lymph nodes, return to the skin and drive a poison ivy rash?

T cells treat skin proteins altered by the oil as foreign and attack them, so the rash is the immune system's overreaction, not damage done by the sap itself.

Poison ivy leaves are green in summer, but what colour are the young leaves that unfold in spring?

Reddish new growth gives way to summer green, and the same leaves blaze yellow, orange or red before they drop in autumn.

Western poison ivy, a separate species from the eastern kind, differs most visibly in which way?

It does not climb: western poison ivy stays a low, upright shrub and creeps outward by underground stems, so it is never the hairy rope on a tree trunk.

Which pantry powder, a cup stirred into a warm bath, do dermatologists suggest for poison ivy itch?

Baking soda counts as a skin protectant under US drug rules, easing minor irritation and itching while the rash runs its course over a week or two.

Besides soapy water, which household liquid do dermatologists say can wash poison ivy oil off skin?

Rubbing alcohol can lift the oil, but speed matters: wash straight after touching the plant and some of it comes away before it reaches other skin or other people.