This list covers 10 poisons that start with the letter U, running from “Urushiol” to “Urginea glycosides.” They come from a wide range of sources, including plants, fungi, metals, and synthetic chemicals, and most of them cause harm through skin contact, ingestion, or inhalation. Some show up in nature as a plant’s natural defense, while others are byproducts of industry or even rocket fuel.
Poisons are substances that damage the body or disrupt how it works, sometimes in small doses and sometimes only after heavy exposure. Many of the “U” poisons have surprising backstories, like Upas, a Southeast Asian tree sap once used to coat blowgun darts because it could stop a heart within minutes. Others, like urushiol from poison ivy, are far more common and cause a familiar itchy rash rather than a life-threatening reaction.
Below you’ll find the table with Poison, Source, Effects, Antidote, and Description.
Poison: the name of the toxic substance, so you can quickly identify which “U” poison you’re looking at.
Source: where the poison comes from, whether it’s a plant, fungus, mineral, or man-made chemical, so you know how exposure typically happens.
Effects: the health problems the poison causes, from mild irritation to serious organ damage, so you understand the risks involved.
Antidote: the treatment or response used against the poison, letting you know whether a specific antidote exists or only supportive care is available.
Description: a short explanation of what the poison is and why it matters, giving you context beyond the raw facts in the other columns.
Poisons
| Poison | Source | Effects | Antidote |
|---|---|---|---|
| Urushiol | Sap and oils of poison ivy, poison oak, and poison sumac plants | Severe allergic contact dermatitis with itching, redness, and blistering | No true antidote; topical corticosteroids and antihistamines ease symptoms |
| Upas | Latex sap of the Upas tree (Antiaris toxicaria), Southeast Asia | Cardiac arrest caused by disrupted heart muscle contractions | No specific antidote; supportive cardiac care |
| Uranium | Naturally occurring radioactive heavy metal ore and its compounds | Kidney damage from chemical toxicity plus long-term cancer risk from radiation | Chelation therapy, such as sodium bicarbonate, to protect the kidneys |
| Urethane | Byproduct of fermentation in bread, wine, and soy sauce; also made industrially | Recognized carcinogen; nervous system depression and breathing failure at high doses | No specific antidote; supportive treatment |
| Usnic acid | Extracted from lichens, sometimes added to weight-loss supplements | Severe liver toxicity, occasionally leading to liver failure | No specific antidote; stop exposure and provide liver-supportive care |
| Ustiloxins | Produced by the fungus Ustilaginoidea virens, which infects rice | Cell and organ damage, particularly to the liver and spleen | No specific antidote; supportive treatment |
| Umbellulone | Volatile oil in the leaves of the California bay laurel (Umbellularia californica) | Intense headaches, sinus and eye irritation, breathing difficulty from fumes | No antidote; remove from exposure and treat symptoms |
| Uzarin | Extracted from the root of the African Uzara plant (Xysmalobium undulatum) | Heart rhythm disturbances, nausea, and vomiting at high doses | Digoxin immune Fab (antibody fragments) for severe cases |
| Unsymmetrical dimethylhydrazine | Synthetic chemical used as rocket propellant | Liver, kidney, and nervous system damage; suspected carcinogen | No specific antidote; pyridoxine (vitamin B6) may help with seizures |
| Urginea glycosides | Bulb of the sea squill plant (Urginea maritima), native to the Mediterranean | Vomiting and dangerous heart rhythm changes, especially in animals | Digoxin immune Fab for severe cardiac glycoside poisoning |