Poison ivy was sent to Europe in the 1600s as an exotic, ornamental oddity

Poison ivy's characteristic rash is caused by an allergic response to an oily compound in the plant called urushiol

Chinese lacquer tree sap also contains urushiol, yet the sap was widely used as a lacquer in Asian lacquerware for thousands of years. The word "urushiol" is derived from the Japanese word "usushi," which is the word for the lacquer tree.

Poison ivy's characteristic rash is caused by an allergic response to an oily compound in the plant called urushiol.

Poison ivy's rash-causing compound is found in the plant's roots, stem, and leaves—so coming into contact with any part of the plant can lead to rashes for the 85% of people who are allergic to it

Once sold as an ornamental plant, poison ivy can actually look varied—its colors change seasonally from reddish to green to yellow. It typically has three broad, shiny, tear-shaped leaves. But it sometimes may have a different number of leaves, and its edges can be serrated.

During the French Revolution, a botanist's letter asking about "dear Rhus" (poison ivy) was intercepted and led to authorities' suspicions he was conspiring with the Russians

The 1794 incident involved André-Ignace-Joseph Dufresnoy, a French army physician researching the plants' potential medicinal properties. Rhus radicans is a scientific name for the plant, though it's commonly called Toxicodendron radicans.

Poison ivy's rash-causing compound is found in the plant's roots, stem, and leaves—so coming into contact with any part of the plant can lead to rashes for the 85% of people who are allergic to it.

Scientists testing how climate change affected plants found in a years-long simulation study that poison ivy grew 70% faster than it did without extra carbon dioxide

The experiments in the 1990s were designed to simulate potential 2050 conditions, using carefully controlled circular forest plots with gas pumped into them.

During the French Revolution, a botanist's letter asking about "dear Rhus" (poison ivy) was intercepted, leading authorities to suspect he was conspiring with the Russians.

Between 10 million and 50 million people in the US develop rashes from poison ivy, poison sumac, and poison oak each year.

This poison ivy knowledge quiz—accompanied by photos of the plant's varied forms—may help you identify this common rash-inducing growth.

Poison ivy is in the same family as mangoes, cashews, and pistachios—and they all produce oily urushiol in their raw, unprocessed state—but they are typically prepared in ways to avoid causing human discomfort.

Urushiol, the oily toxin in poison ivy, can remain allergenic on clothing for years.

Scientists testing how climate change affects plants found, in a years-long simulation study, that poison ivy grew 70% faster with the resulting extra carbon dioxide.

The pharmaceutical industry evolved, in part, from the discovery of synthetic dyes

In 1856, a chemist accidentally discovered mauveine, the world’s first synthetic dye, while trying to make quinine to treat malaria. The synthetic dyes that followed helped reveal germs under microscopes, paving the way for modern imaging techniques and breakthrough treatments, such as antibiotics.

Poison frogs get their toxins from eating insects and mice

Other animals, including royal ground snakes, are able to survive eating poison. Scientists study the creative antitoxin defenses in these animals to discover treatments for poisoning.

The expedition documented 240 plant species, 178 new to western science

Lewis and Clark’s botanical records introduced species to Americans like bitterroot, ponderosa pine, and Oregon grape—plants unknown to western science at the time. See a selection of these species in this image gallery.

Wood that changed the color of water was the earliest recorded example of fluorescence

Lignum nephriticum, a tea used to treat kidney and urinary illnesses, was described in the 16th century as derived from white wood that turned water a bluish hue. However, in the 17th century, accounts described the wood as reddish and creating a kaleidoscope of colors in water. In 1915, the sources were identified as two different woods, which absorb UV radiation and emit visible light.

Eliza Scidmore advocated for planting cherry trees in Washington, DC, in the early 1900s

The first female writer for National Geographic, Scidmore championed planting Japanese cherry trees around the Tidal Basin in Washington, DC. Her idea succeeded in 1912, after years of lobbying, creating one of the National Mall's most enduring traditions and tourist draws.

Evidence of opium use dates to as early as 5000 BCE

Archaeological evidence shows the use of the poppy plant for its pain-killing properties likely originated in the Mediterranean before making its way to the East and West via trade. It has since inspired two eponymous wars, and highly addictive derivatives of the naturally occurring substance have led to an ongoing overdose crisis.

When a Paris department store hesitated to sell Estée Lauder's perfume, she 'accidentally' broke a bottle, causing the smell to spread throughout the store and shoppers to start asking to buy the scent.

Edward Jenner, the father of vaccinations

The British physician was the first to attempt to inoculate someone from smallpox using its milder cousin, cowpox. His innovations and documentations would prove crucial to the deployment of widespread vaccinations.

A root lice infestation once destroyed over 80% of Napa's vines

In the late 1860s, an infestation of root lice nearly destroyed the global wine industry. European rootstock, now planted across multiple continents, had no natural defenses against the pests, which infected the vines (as seen below). As a result, more than 80% of Napa’s vines were destroyed by 1900. It took decades for the industry to recover.

Volcanoes in the 1340s likely helped trigger the Black Death

The "bubonic plague" that wiped out roughly half of Europe and Asia originated from many factors. Recent research suggests volcanic eruptions contributed as well. The "aerosol" effects of matter released from eruptions likely prompted famine and accelerated the spread of infected fleas riding on grains avoiding spoilage.

In 1951, a small French town was overtaken by the fungus that ultimately led to LSD

During the summer of 1951, the French town of Pont-Saint-Esprit appeared to go mad. Hundreds were treated for hallucinations and delirium, with some reporting ongoing hallucinations a month after the LSD-like symptoms appeared. Some historians argue it was a case of ergotism, better known in the Middle Ages as "burning disease" and "St. Anthony's Fire."

The diplomat who implemented Monroe's policy introduced the poinsettia to the United States

Joel Roberts Poinsett, appointed as the first US minister to Mexico in 1825 following the doctrine's announcement, took cuttings of a vibrant Mexican plant called the cuetlaxochitl during his time there. Americans loved the foliage and named it after him.

'Roses are red, violets are blue' has a long, twisting history

The earliest known use of the phrase, a stock romance form used in greeting cards, is in Edmund Spenser's "The Faery Queen" from 1590 (excerpt below). By 1785, Joseph Ritson updated the verse and connected it to Valentine's Day, creating a cliché that's still used today.

The mystery of the cucumber, from coiling tendrils to its bitter, mature fruit

Cucumus sativus was first cultivated 3,000 years ago in the Himalaya of India, appearing in ancient Sanskrit hymns in the Hindu tradition. They are typically harvested well before maturation, as their yellow, final fruit is bitter. Their coiling tendrils were so distinct they prompted famed naturalist Charles Darwin to publish one of his lesser-known works, "On the Movements and Habits of Climbing Plants." Its refreshing coolness inspired cucumber-derived body washes and sprays over millennia.

The International Olympic Committee banned ibogaine decades ago

Beyond use by athletes as a stimulant before the ban, the drug has a long history. The psychoactive substance was also mass produced in the mid-20th century by a French pharmaceutical company as a product called Lambarène, which was marketed as a cure for conditions including depression and lethargy. Production halted in 1966, however, when ibogaine-containing products became illegal in France.

Estée Lauder once broke a bottle of the hit perfume 'Youth Dew' to convince French department stores to carry the product

Youth Dew, originally launched in 1953 as a bath oil, was wildly successful in the American market and one of the early products that cemented Estée Lauder as a luxury cosmetics brand. When the Galeries Lafayette in Paris hesitated to sell the perfume, Lauder "accidentally" broke a bottle of Youth Dew, causing the smell to spread throughout the department store. Shoppers began asking for the scent, and the department store agreed to sell it.

Queen Victoria and Prince Albert popularized the Christmas tree in 1840s Britain

An 1848 engraving of Queen Victoria and Prince Albert around a decorated Christmas tree sparked a trend across Britain and the US. Their German-inspired custom quickly became a fashionable centerpiece of holiday celebrations.

How Van Gogh painted 'Irises' in an asylum

Van Gogh’s painting titled “Irises” (1889) remains one of his most-recognized works. Created soon after the artist checked himself into an asylum, the oil painting depicts flowers from the overgrown garden in the institution. Discover more about the work and other masterpieces Van Gogh constructed during a personally tumultuous time.

View the model of the tobacco mosaic virus from the 1958 Brussels World's Fair

After she finished analyzing her X-ray diffraction data on DNA fibers, Rosalind Franklin explored plant virus structures. For her work on the TMV, she was invited to build this 5-foot model, modified from earlier versions made of ping pong balls and bicycle handlebar grips.

Leprosy has been detected in British red squirrels

The animals have been infected with both strains of the bacterium that cause leprosy. Researchers have found that squirrels living in different parts of the UK were infected with different species of the disease-causing bacteria. (Some users may experience a paywall.)

Volcanic activity may have triggered the Black Death by spewing gases that led to crop failures in Europe, thus forcing the import of grain ships with plague-infested fleas.

Japanese artwork often incorporates bold colors, clean lines, and natural subjects

While Japanese art is diverse and continues to adopt new styles and techniques, the Japanese approach to painting nature inspired Georgia O’Keeffe, who was known for depicting the environment in a detailed yet realistic manner. Below is "The Great Wave off Kanagawa," from 1931, by Hokusai.

The Judgment of Paris was organized by Steve Spurrier

The English wine merchant organized the competition with Patricia Gallagher at his Paris wine shop. In this in-depth interview, he talks about how he got into the wine trade, how the Judgment of Paris impacted his own career and the global wine scene, and tells some of his favorite stories from the past.

At the beginning of the 20th century, a group of young men ate standard American food—replete with food additives like borax and formaldehyde—as part of government research to better understand food safety.

Graffiti dates back to at least ancient Pompeii, where citizens scrawled messages to one another on public walls

The 19th-century painters of the Hudson River School were among the first American romantics, with portraits that displayed the natural beauty of the young country.

Learn more about the history of fireworks, which dates back to an accidental invention during an alchemist's quest for information about immortality.

Georgia O'Keeffe's flower paintings are often assumed to be sexual, though the artist claimed she was simply interested in highlighting the beauty of flowers that most people neglect

Many legends about George Washington, including his supposed wooden teeth and the story of cutting down the cherry tree, lack evidence.

The American cockroach is actually from Africa, an apparent hitchhiker aboard ships carrying enslaved people, with evidence suggesting the bug may have arrived in the New World as early as the 1600s.

See the evolution of Ebola vaccine and treatment development.

'Shogun,' a 1980s TV series, helped popularize sushi in the US by stimulating an American interest in Japanese culture.

Some Pokémon have been named after real and fictional organisms, while some real-world species have been named after Pokémon, such as Chilicola charizard and Binburrum zapdos.

Sunflowers have long been a symbol of nuclear disarmament because they can extract large amounts of radioactive cesium from soil.

The concept of phantom limbs, the perception that amputated limbs are still present, dates back to a French military surgeon in the 16th century.

Louisiana's 'Cancer Alley' is infamous for having some of the highest industrial pollution, toxic air emissions, and cancer risks in the US.

The term 'algorithm' originated from the Latinized name of al-Khwārizmī, a 9th-century mathematician whose works introduced Arabic numerals and the decimal-based numeral system to Europe and whose treatise 'Al-Jabr' gave algebra its name.

In 2019, a laptop loaded with six of the worst malware in history and described as 'an exhibit of historical weaponry' sold for $1.3M.