This list covers 12 poisons with names starting with the letter Y, ranging from “Yew” to “Yellow Bells.” Most come from plants, shrubs, and trees that grow in gardens, forests, or the wild, though a few are minerals or man-made chemicals. People encounter them through ornamental landscaping, old household products, herbal supplements, and even contaminated seafood.

Poisons are substances that harm or kill a living organism when they enter the body in sufficient amounts. Many of the entries here come from plants once used in traditional medicine or folklore, like yohimbine bark, which was historically brewed as a stimulant tonic long before its risks were understood. Others, like Yperite, carry a darker history tied to chemical warfare.

Below you’ll find the table with each poison’s source, effects, antidote, and description.

Poison: the common name of each poisonous substance, so you can quickly identify what you’re looking up.

Source: where the poison comes from, such as a specific plant, mineral, or man-made product, helping you recognize it in real life.

Effects: the symptoms a person or animal may experience after exposure, so you understand the risks involved.

Antidote: the treatment or medical response used to counteract the poison, letting you know what options exist if exposure happens.

Description: a short overview explaining what the poison is and why it’s notable, giving you extra context beyond the basic facts.

Poisons

PoisonSourceEffectsAntidote
YewYew tree (Taxus baccata) needles and seedsNausea, dizziness, irregular heartbeat, cardiac arrestNo specific antidote; activated charcoal and supportive cardiac care
Yellow OleanderYellow oleander shrub (Thevetia peruviana) seeds and sapVomiting, irregular heartbeat, dangerously slow pulseDigoxin-specific antibody fragments (Digibind)
Yellow JessamineYellow jessamine vine (Gelsemium sempervirens) flowers and rootsMuscle weakness, drooping eyelids, breathing failureNo specific antidote; supportive respiratory care
YperiteSynthetic chemical warfare agent (sulfur mustard)Skin blistering, blindness, lung damageNo specific antidote; immediate decontamination and supportive care
YessotoxinMarine algae toxin absorbed by shellfishNausea, in high doses possible heart tissue damageNo specific antidote; supportive care
Yellow PhosphorusOld-style matches, fireworks, some rodenticidesVomiting, liver failure, garlic-smelling breathNo specific antidote; supportive care and liver monitoring
YohimbineBark extract of the African yohimbe treeRacing heart, high blood pressure, anxiety, seizuresNo specific antidote; supportive care and blood-pressure management
Yellow ArsenicOrpiment mineral (arsenic trisulfide)Stomach pain, vomiting, multi-organ damageDimercaprol (BAL) or DMSA chelation therapy
Yellow StarthistleYellow starthistle plant (Centaurea solstitialis)In horses: brain damage, difficulty eating (“chewing disease”)No specific antidote; supportive care
Yellow StainerYellow stainer mushroom (Agaricus xanthodermus)Stomach cramps, vomiting, diarrheaNo specific antidote; supportive care
Yellow IrisYellow iris plant (Iris pseudacorus) rhizome and sapSkin irritation, nausea, vomitingNo specific antidote; supportive care
Yellow BellsYellow bells shrub (Tecoma stans) leaves and seedsVomiting, diarrhea, low blood sugarNo specific antidote; supportive care

Descriptions

Yew
A common evergreen tree whose needles and seeds contain taxine alkaloids that can stop the heart if enough is eaten. Even a handful of crushed seeds can be fatal to humans and livestock.
Yellow Oleander
A tropical ornamental shrub whose seeds contain heart-stopping cardiac glycosides similar to digoxin. It’s one of the most common plant poisonings in parts of Asia.
Yellow Jessamine
A fragrant flowering vine popular in gardens whose gelsemine alkaloids paralyze muscles and can shut down breathing if chewed or brewed into tea.
Yperite
Also known as mustard gas, this oily chemical weapon was first used near Ypres, Belgium, in World War I and causes severe chemical burns on contact.
Yessotoxin
A toxin produced by certain ocean plankton that builds up in mussels and other shellfish, sometimes prompting seafood harvest closures.
Yellow Phosphorus
A highly reactive form of phosphorus once common in matches, capable of causing severe liver and organ damage if swallowed.
Yohimbine
An herbal stimulant sold as a supplement that, in excess, overstimulates the nervous system and can trigger dangerous spikes in heart rate and blood pressure.
Yellow Arsenic
A bright yellow arsenic-based mineral historically used as a pigment and, unfortunately, as a poison, causing classic arsenic toxicity symptoms.
Yellow Starthistle
A spiky yellow-flowered weed that’s especially dangerous to horses, whose repeated grazing on it can permanently damage the brain’s chewing control center.
Yellow Stainer
A wild mushroom that resembles the edible field mushroom but bruises yellow when cut and causes unpleasant gastrointestinal poisoning if eaten.
Yellow Iris
A striking yellow-flowered wetland plant whose sap and rhizome contain irritant glycosides that upset the stomach and can blister skin on contact.
Yellow Bells
A popular yellow-flowering ornamental shrub whose leaves and seeds contain compounds that can cause digestive upset and dangerously low blood sugar if ingested.
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