This list covers 31 poisons, from “Habu Snake Venom” to “Hypericin.” You’ll find venoms from snakes and spiders, toxic plants and berries, industrial chemicals, and prescription drugs that turn dangerous in overdose. Some come from nature and defend animals or plants from predators, while others are man-made compounds used in medicine, manufacturing, or agriculture before their risks were fully understood.
Poisons are substances that harm or kill living tissue when they enter the body, whether through a bite, a meal, or simple skin contact. Some act in minutes, like hydrogen cyanide gas once used in execution chambers, while others build up slowly over years of low-level exposure. Many were once common in homes and hospitals before science caught up with their hidden dangers.
Below you’ll find the table with the poison, source, effects, antidote, and description.
Poison: the common name of each substance, so you can quickly find the one you’re looking for.
Source: where the poison comes from, whether it’s a plant, animal, chemical, or drug.
Effects: the symptoms and health problems the poison causes in the body.
Antidote: the treatment or remedy used to counter the poison, when one exists.
Description: a short explanation of what the poison is and why it matters.
Poisons
| Poison | Source | Effects | Antidote |
|---|---|---|---|
| Habu Snake Venom | Habu pit viper (Protobothrops flavoviridis), Japan | Local swelling, tissue necrosis, bleeding disorders | Habu-specific antivenom |
| Halothane | Inhaled anesthetic gas | Liver damage, hepatitis, low blood pressure | No specific antidote; supportive care |
| Hammerhead Flatworm | Bipalium land planarian secretions | Nausea if ingested; neurotoxic to prey | None specific |
| Heliotrope | Heliotropium plant (pyrrolizidine alkaloids) | Liver damage, veno-occlusive disease | None specific; supportive care |
| Hellebore | Helleborus plant (cardiac glycosides) | Vomiting, irregular heartbeat, seizures | None specific; supportive care |
| Hemlock | Poison hemlock, Conium maculatum | Muscle paralysis, respiratory failure | No antidote; activated charcoal, ventilation support |
| Hemlock Water Dropwort | Oenanthe crocata plant | Violent seizures, cardiac arrest | None specific; benzodiazepines for seizures |
| Henbane | Hyoscyamus niger plant | Hallucinations, delirium, rapid heartbeat | Physostigmine |
| Heptachlor | Organochlorine pesticide | Tremors, seizures, liver damage | None specific; supportive care |
| Heroin | Illicit opioid drug (diacetylmorphine) | Respiratory depression, coma, death | Naloxone |
| Hexachlorophene | Antibacterial chemical compound | Neurotoxicity, brain swelling in infants | None specific; supportive care |
| Hexane | Industrial solvent | Peripheral nerve damage, numbness | None specific; remove exposure |
| Hexavalent Chromium | Industrial chromium compound | Lung cancer, organ damage | None specific; supportive care |
| Histamine (Scombrotoxin) | Spoiled fish (tuna, mackerel) | Flushing, headache, digestive upset | Antihistamines |
| Hoary Alyssum | Berteroa incana plant | Laminitis and fever in horses | None specific; veterinary supportive care |
| Hobo Spider Venom | Hobo spider, Eratigena agrestis | Local pain, swelling (necrosis disputed) | None specific |
| Hogweed, Giant | Heracleum mantegazzianum sap | Severe skin burns, blistering | None; avoid sunlight, wash skin |
| Holly Berries | Ilex plant berries | Vomiting, diarrhea, drowsiness | None specific; supportive care |
| Hooded Pitohui | Pitohui dichrous, New Guinea | Numbness, tingling on contact | None specific |
| Horse Chestnut | Aesculus hippocastanum seeds | Vomiting, weakness, uncoordination | None specific; supportive care |
| Horsetail | Equisetum plant | Vitamin B1 deficiency, weakness in livestock | Thiamine |
| Hyacinth Bulbs | Hyacinthus plant bulbs | Nausea, vomiting, skin irritation | None specific; supportive care |
| Hydrazine | Rocket fuel and industrial chemical | Seizures, liver and kidney damage | Pyridoxine (vitamin B6) |
| Hydrofluoric Acid | Industrial and glass-etching chemical | Severe burns, dangerously low calcium | Calcium gluconate |
| Hydrogen Cyanide | Industrial gas, combustion byproduct | Cellular asphyxiation, rapid death | Hydroxocobalamin |
| Hydrogen Peroxide (Concentrated) | Industrial bleaching chemical | Tissue burns, gas embolism | None specific; supportive care |
| Hydrogen Sulfide | Sewage and volcanic gas | Respiratory paralysis, loss of consciousness | Nitrites, oxygen therapy |
| Hydromorphone | Prescription opioid drug | Respiratory depression, sedation, coma | Naloxone |
| Hydroquinone | Skin-lightening chemical | Skin darkening (ochronosis), blood disorders | Methylene blue (for methemoglobinemia) |
| Hyoscyamine | Nightshade plant alkaloid | Dry mouth, hallucinations, rapid pulse | Physostigmine |
| Hypericin | St. John’s Wort compound | Photosensitivity, skin burns in sunlight | None specific; avoid sun exposure |
Descriptions
Habu Snake Venom
Venom from Okinawa’s habu snake, a pit viper whose bite causes intense swelling and can destroy tissue around the wound if untreated.
Halothane
A general anesthetic once common in surgery, now rarely used because repeated exposure can trigger severe, sometimes fatal liver inflammation.
Hammerhead Flatworm
An invasive worm-like predator that secretes tetrodotoxin, the same nerve poison found in pufferfish, to subdue earthworms and snails.
Heliotrope
A flowering plant whose alkaloids slowly damage the liver when eaten regularly, historically causing poisoning through contaminated grain and herbal teas.
Hellebore
Also called the Christmas rose, this garden plant contains heart-affecting compounds that can cause severe vomiting and dangerous arrhythmias if eaten.
Hemlock
The plant that killed Socrates, hemlock’s coniine alkaloid shuts down the nervous system, causing paralysis that spreads until breathing stops.
Hemlock Water Dropwort
Considered one of Britain’s most toxic plants, its root resembles a parsnip but contains oenanthotoxin, which triggers seizures within minutes of ingestion.
Henbane
A nightshade relative used in ancient medicine and witchcraft lore, henbane’s alkaloids cause vivid hallucinations and can be fatal in higher doses.
Heptachlor
A once-popular insecticide banned in most countries after studies linked it to seizures, liver harm, and long-term cancer risk.
Heroin
A fast-acting opioid derived from morphine; overdose slows breathing until it stops entirely, making it a leading cause of accidental poisoning deaths.
Hexachlorophene
Once used in soaps and baby powders, this antiseptic was restricted after it was found to cause brain damage in infants absorbing it through skin.
Hexane
A petroleum-derived solvent used in glues and industrial cleaning; inhaling its fumes over time damages nerves in the hands and feet.
Hexavalent Chromium
Famously linked to contaminated groundwater in the Erin Brockovich case, this industrial byproduct damages DNA and raises cancer risk with prolonged exposure.
Histamine (Scombrotoxin)
Improperly refrigerated fish lets bacteria convert its amino acids into histamine, causing an allergic-like reaction known as scombroid poisoning within minutes of eating.
Hoary Alyssum
A weedy field plant that’s harmless to humans but can cause painful hoof inflammation and fever in horses that eat contaminated hay.
Hobo Spider Venom
A Pacific Northwest spider once blamed for necrotic bites, though modern research suggests its venom rarely causes more than mild local irritation.
Hogweed, Giant
This towering invasive plant’s sap contains chemicals that react with sunlight to cause painful, blistering burns on any skin it touches.
Holly Berries
The cheerful red berries of the holiday plant are mildly toxic, causing stomach upset and nausea in children or pets who eat more than a few.
Hooded Pitohui
One of the few known poisonous birds, its skin and feathers carry batrachotoxin, a nerve toxin absorbed from its insect diet.
Horse Chestnut
The shiny brown “conkers” of this ornamental tree contain aesculin, a compound that causes stomach upset if eaten raw and unprocessed.
Horsetail
An ancient, primitive plant containing an enzyme that destroys thiamine, gradually poisoning grazing animals that eat large amounts of it.
Hyacinth Bulbs
The fragrant spring bulb contains irritating calcium oxalate crystals that cause stomach upset and contact dermatitis when handled or eaten.
Hydrazine
A highly reactive chemical used in rocket propellant, hydrazine exposure can trigger seizures and organ damage, treated much like INH overdose.
Hydrofluoric Acid
Deceptively mild-looking, this acid penetrates skin painlessly at first, then leaches calcium from the body, which can stop the heart.
Hydrogen Cyanide
A fast-acting gas that blocks cells from using oxygen; famously used in gas chambers and released by burning certain plastics.
Hydrogen Peroxide (Concentrated)
While diluted household peroxide is harmless, industrial-strength concentrations can burn tissue and release oxygen gas bubbles into the bloodstream.
Hydrogen Sulfide
Known for its rotten-egg smell, this gas quickly numbs the sense of smell and can paralyze breathing at high concentrations, killing within minutes.
Hydromorphone
A potent painkiller several times stronger than morphine; overdose slows breathing dangerously, the same mechanism behind most opioid deaths.
Hydroquinone
Used in skin-bleaching creams, this chemical can ironically darken skin with long-term use and, in rare cases, alter how blood carries oxygen.
Hyoscyamine
An alkaloid found in henbane and related plants that blocks nerve signals, causing the classic “mad as a hatter” anticholinergic symptoms.
Hypericin
A pigment in St. John’s Wort that makes skin dangerously sensitive to sunlight, an effect first noticed in grazing animals eating the plant.