Poison ivy was sent to Europe in the 1600s as an exotic, ornamental oddity, where it was purposefully grown in the English royal gardens at Kew, the Faculty of Medicine in Paris, and a few other locations.

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.

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

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.

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

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

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.

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.

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.

Measles reached global transmission during the 15th- and 16th-century Columbian exchange

Devastating diseases like smallpox, influenza, measles, and other viruses were largely introduced into the Western Hemisphere beginning with the 1492 arrival of Christopher Columbus and the ensuing age of exploration.

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.

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."

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.

For centuries, European aristocrats made travel a rite of passage

Starting in the 16th century, young English aristocrats mounted “Grand Tours” of Europe. Accompanying tutors provided lessons in the continent’s architecture, art, history, and literature. A Grand Tour wasn’t just for classical education, though; it was also an opportunity for young men to indulge in vices away from their parents.

American farmers—including George Washington—experimented with coffee farming

Two coffee plants—an arabica strand and a Kentucky Coffee Tree—continue to grow at Mount Vernon, Washington's iconic Virginia home. The Marquis de Lafayette requested the agrarian commander send him some beans in France.

Mini-portraits were shared as love tokens in Elizabethan England

Art historians are identifying previously unknown works by Nicholas Hilliard, Elizabeth I's court painter, whose thumb-sized watercolors on vellum served as love tokens, diplomatic currency, and status symbols. They were believed to be passed secretly between courtiers and monarchs.

Santa Barbara’s Botanic Garden was the first to showcase the state’s native plants

Founded in 1926, the garden’s founders sought to showcase the state’s local flora as a matter of conservation, rather than the water-hungry exotics regularly being imported. This story focuses on how the garden’s design took a more natural and less formal direction.

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.

Oxford scientists turned Fleming’s mold discovery into medicine

In 1939, a team at Oxford—including Howard Florey, Ernst Chain, and Norman Heatley—revived Fleming’s forgotten discovery. Using makeshift equipment like bedpans and milk churns, they purified enough penicillin to prove it could treat deadly infections.

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.

Paris and Boston were redesigned partly to combat cholera's spread

Georges-Eugène "Baron" Haussmann, who oversaw Paris's redesign in the 1800s, replaced many of the city's narrow streets with wide boulevards. This was done at least in part to bring more air and light into the city to help control cholera. Architect Arthur Gilman redeveloped Boston's Back Bay to similarly combat cholera, among other reasons.

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.

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.

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.)

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.

The first ever IPO was issued by the Dutch East India Co., a spice company

It first offered shares to the public in the 1600s on the Amsterdam Stock Exchange to help finance its passages. The Dutch East India Co. succeeded in part due to its monopolistic hold over the East Indies at the time.

View some of the most invasive species in US waters

Introduced in the late 1600s from Eastern Asia, the goldfish is considered the first invasive fish in North America. The venomous lionfish is safe to consume, but catching it is complicated by its reluctance to respond to hook-and-line-style fishing attempts.

The "green men" were among the first European pyrotechnicians

In the 1600s, men wore leaf-covered caps when handling fireworks to protect against sparks. Headgear was also worn by those helping to maintain order when leading medieval fireworks processions, often acting like jesters to entertain viewing audiences.

The history and significance of rosemary

Rosemary is more than just an herb—it’s a powerful symbol intertwined with ancient Egypt, Christianity’s origins, Shakespeare, the culinary arts, and more. Native to the Mediterranean area, this plant has accompanied humanity for centuries, providing us with pleasant aroma, adornment, and even medicine. Explore this article for further insight into the significance of our long-standing relationship with rosemary.

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 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.

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

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

Explore what it's like inside a patient isolation unit, used in situations such as treating a patient or suspected patient with Ebola.

See images of medical cases of firework injuries shared on this 'Instagram for doctors.' (Warning: Graphic content)

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

The original copy of the Declaration of Independence is not a pristine document, and even features a smudged anonymous handprint in the bottom left corner.

The first line of 'immortal' human cells, which can divide indefinitely and are used in scientific research, was nonconsensually taken from a Black woman.

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.

'Grand Canyon of the Yellowstone,' a work by American painter Thomas Moran, inspired Congress to establish Yellowstone National Park.

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.

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

Elk Cloner, the first computer virus to spread in public, was written as a practical joke by Richard Skrenta, a Pittsburgh high school student.