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 substance 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.

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.

Poison ivy is projected to be larger and more resilient due to climate change.

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

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

See if you know how to recognize poison ivy with this quiz.

Urushiol, the oily toxin in poison ivy, can remain allergenic on clothing for up to 5 years—or even longer.

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.

Poison ivy, which produces urushiol throughout the plant, not just in the leaves, can cause year-round rashes.

Some invasive plants, such as English ivy, maiden grass, and Norway maple, can swiftly take over gardens and damage yard structures if left unchecked.

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.

In 1982, around 20% of the people who ate some of the roughly 7,400 bags of cashews sold as part of a Little League fundraiser in Pennsylvania broke out in rashes because of natural urushiol residue on the nuts' shells that hadn't been removed and fully cooked off—the same allergy-inducing substance found in poison ivy.

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 history of iconic pigments used in seven famous paintings

While art paints can be bought by the bucket at any craft store today, pigments throughout history have been difficult to come by. Art historian Kelly Grovier traces the fascinating history of pigments that make up hidden layers in masterpieces from Picasso and Hokusai’s Prussian Blue to Vermeer’s shade of red.

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.

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.

A root lice infestation, transported from the East Coast, once destroyed around 70% of Napa's vines.

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.

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.

Impressionist painter Pierre-Auguste Renoir suffered from arthritis in the 1800s when there were no treatments, and eventually had such limited hand function that he painted with brushes placed in his mouth.

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.

While invasive species typically harm ecosystems by outcompeting native organisms for resources, some provide unexpected benefits, including new shelters, nesting habitats, and reduced environmental heat stress.

The cholera bacteria was first isolated in 1854—but the discovery was largely ignored

The pathogen was isolated by the Italian physician Filippo Pacini in Florence, Italy, though his discovery was largely ignored in favor of the popular miasma—bad air—theory of disease at the time. The pathogen was separately isolated about three decades later by German microbiologist Robert Koch.

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.

'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.

A French Army surgeon discovered that malaria is a parasitic disease in 1880—but scientists were initially skeptical.

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.

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

Rosalind Franklin uncovered the molecular structure of the tobacco mosaic virus

Franklin's work revealed the role of ribonucleic acid in virus infectivity, contributing to a foundational understanding of genetics and virology. Her molecular model of the virus was featured as the centerpiece at the 1958 Brussels World's Fair.

Natural toxins produced on plants or consumed by animals may cause food poisoning

When humans eat plants with certain natural toxins on them—including a family of toxins called aflatoxins that fungi produce on crops like peanuts and corn— they can become ill with food poisoning. Toxins can still harm humans even if animals or plants appear fine to the human eye. The World Health Organization advises that we should throw away moldy or discolored foods, refrain from eating wild plants or mushrooms that aren’t definitively nonpoisonous, and remember that just because something is “natural” it’s not always safe to eat.

Aspirin was the first synthesized anti-inflammatory drug

Once used by the ancient Sumarians—extracted from willow bark—but now synthesized in the lab, the active ingredient of this popular medication has been used to treat headaches and pain for thousands of years.

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.

Vanilla was originally used as an additive in chocolate rather than as a standalone flavor.

Morphine, heroin, codeine, and more were derived from opium

Opium reached the US at about the time early colonists were itching for ways to soothe aches and pains. The active ingredient in the substance was isolated in the early 19th century, eventually leading to the manufacture and commercial sale of morphine, heroin, and other opium-based drugs.

The story of the Radium Girls, who exposed the dangers of radioactive paint

After radium was discovered in 1898, companies began using radium-based paints on watch and clock dials to create a glow-in-the-dark effect. Women who worked to apply the paint were encouraged to use their lips and tongues to help create the fine point needed to draw small numbers, unknowingly poisoning themselves.

The legacy of Agent Orange: a photo gallery

An herbicide sprayed over the Vietnamese jungles during the war had a far greater impact than its supposed role as a defoliant, a chemical used to remove greenery. Agent Orange’s deleterious nature quickly impacted exposed people – and their children. This photo gallery, which includes graphic images, follows a photographer as they report on those affected by the chemical.

The virus was officially described for the first time in 1789

Michael Underwood, an English physician and surgeon, was the first to describe the disorder, noting it caused disability in the lower extremities in children. Large-scale outbreaks of the disease were not observed until the late 19th century.

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.

Rome's herbal panacea may not be as extinct as we thought

Silphion: cure-all, aphrodisiac, birth control, tasty seasoning. Nero allegedly ate the last of this miracle plant. This article details how a researcher may have found more. Seven centuries after the yellow-flowered plant was first documented growing in what's now Libya, it vanished. Historians proposed that the loss of Silphion may have been the first recorded extinction of any species.

Plants use physical and chemical defenses to protect themselves

Tree bark is difficult to chew and resistant to pathogens, while the waxy cuticle on the surface of leaves deters insects and microbes. Some plants possess thorns, spines, and prickles to discourage predators. Plant cells can also produce antimicrobial toxins or release compounds to alert parasitic wasps to lay eggs in attacking insects.

Opium's history traces from religious use to mass-market commercial products

Religious or medical use of opium was present across Europe and Asia as early as 5000 BCE. By the 16th century, humanity had come to see opium as more than medicine: It was a marketable product. This perspective also defines today's relationship with opioids, highly addictive painkillers at the heart of an ongoing drug crisis.

Recent research indicates leprosy was present in the Americas before European settlers

New research published in 2025 upended long-held notions that the disease was introduced to the Americas by European colonizers. Evidence of a lesser-known leprosy-causing bacterium was found in ancient human remains that date back 4,000 years.

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.

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.

Pigments in paint can come from rocks, plants, insects or synthetic sources

Paint's composition is varied through the combination of pigments with binding agents. In the past, artists created their own paints by mixing pigments with water, oils or egg yolks to bind the colors together.

The 'definitive' history of magic mushrooms

Where did magic mushrooms come from, and how did they get their magical reputation? This article explains the history of the psychedelic fungi from pre-history to now. The earliest concrete evidence of psychedelic mushroom use is 12,000-year-old murals in Northern Australia that portray mushroom iconography. Considering how many species seek out and consume psychoactive substances, such as Siberian reindeer, it's possible human use of these psychedelic mushrooms may predate these murals.

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.