poisoning include lack of appetite, depression, constipation, diarrhea (which may contain blood), blood in urine, and colic; it is rarely fatal, however, and in fact after proper processing acorns are consumed as a staple food in many parts of the world. rhamnus cathartica commonly called buckthorn. the seeds and leaves are mildly poisonous for people and animals, but are readily eaten by birds. rhododendron spp. several species including those known as azalea. all parts are poisonous and cause nausea, vomiting, depression, breathing difficulties, and coma, though it is rarely fatal. the primary source of toxicity is a group of closely related compounds called grayanotoxins, which block sodium ion channels in cellular membranes and prevent electrical repolarization during action potentials. honey made from the nectar of rhododendron plants may contain dangerous concentrations of grayanotoxins, and has been historically used as a poison and in alcoholic drinks. rhododendron ferrugineum commonly called alpenrose, snow-rose, or rusty-leaved alpenrose. it is moderately toxic, containing arbutin, arecoline and rhodoxanthin, and can cause vomiting, and difficulties of the digestive, nervous, respiratory and circulatory systems. rhododendron luteum also known as yellow azalea or honeysuckle azalea. despite the sweet perfume of the flowers, the nectar is toxic, containing grayanotoxin; records of poisoning of people eating the honey date back to the 4th century bc in classical greece. rhododendron tomentosum commonly known as marsh labrador tea or wild rosemary. all parts of the plant contain poisonous terpenes that affect the central nervous system. first symptoms of overdose are dizziness and disturbances in movement, followed by spasms, nausea, and unconsciousness. the mere smell of the plant may cause headache to some people. rhus spp. certain species commonly known as african sumac. formerly grouped with poison ivy and the rest of the toxicodendron genus, all parts of this tree contain low levels of a highly irritating oil with urushiol. skin reactions can include blisters and rashes. the oil spreads readily to clothes and back again, and has a very long life. infections can follow scratching. as urushiol is not a poison but an allergen, it will not affect certain people. the smoke of burning rhus lancia can cause reactions in the lungs, and can be fatal. ricinus communis commonly known as castor oil plant, castor bean, and palma christi. the seeds contain ricin, an extremely toxic and water-soluble ribosome-inactivating protein; it is also present in lower concentrations in other parts of the plant. also present are ricinine, an alkaloid, and an irritant oil. according to the 2007 edition of the guinness book of world records, the castor oil plant is the most poisonous in the world, though its cousin abrin, found in the seeds of the jequirity plant, is arguably more lethal. castor oil, long used as a laxative, muscle rub, and in cosmetics, is made from the seeds, but the ricin protein is denatured during processing. ricin quickly and irreversibly inhibits ribosomes, the molecular machines responsible for producing proteins in all cells. the ld50 in adults is only about 22 μg/kg when injected or inhaled; ingested ricin is much less toxic due to the digestive activity of peptidases, although a dose of 20 to 30 mg/kg, or about 4 to 8 seeds, can still cause death via this route. reports of actual poisoning are relatively rare. if ingested, symptoms may be delayed by up to 36 hours but commonly begin within 2–4 hours. these include a burning sensation in the mouth and throat, abdominal pain, purging, and bloody diarrhea. within several days there is severe dehydration, a drop in blood pressure and a decrease in urine. unless treated, death can be expected to occur within 3–5 days; if they have not died by this time, they often recover. toxicity varies among animal species: 4 seeds will kill a rabbit, 5 a sheep, 6 an ox or horse, 7 a pig, and 11 a dog. ducks have shown substantial resistance to the seeds: it takes an average of 80 to kill them. poisoning occurs when animals ingest broken seeds or break the seed by chewing; intact seeds may pass through the digestive tract without releasing the toxin. robinia spp. also known as black locust and false acacia. all species produce toxic lectins. the poison is a complex mix of lectins with the highest concentration in the fruits and seeds, followed by the root bark and the flowers. there is little poison in the leaves. the lectins, generally called robin, are less toxic than those of e.g. abrus (abrin) or ricinus (ricin), and in non-fatal cases the toxic effects tend to be temporary. sambucus spp. commonly known as elder or elderberry. the roots, twigs, leaves, and unripe fruit are considered poisonous and cause nausea and digestive upset. ripe berries must be cooked before consumption. sanguinaria canadensis commonly known as bloodroot. the rhizome contains morphine-like benzylisoquinoline alkaloids, primarily the toxin sanguinarine. sanguinarine kills animal cells by blocking the action of na+/k+-atpase transmembrane proteins. as a result, applying s. canadensis to the skin may destroy tissue and lead to the formation of a large scab called an eschar. although applying escharotic agents, including s. canadensis, to the skin is sometimes suggested as a home treatment for skin cancer, these attempts can be severely disfiguring, as well as unsuccessful. case reports have shown that in such instances tumors have recurred and/or metastasized. the united states food and drug administration (fda) has approved the inclusion of sanguinarine in toothpastes as an antibacterial or anti-plaque agent, although it is believed that this use may cause leukoplakia, a premalignant oral lesion. the safe level of sanguinarine in such products is subject to regulation and debate. s. canadensis extracts have also been promoted by some supplement companies as a treatment or cure for cancer, but the fda has listed some of these products among its "187 fake cancer 'cures' consumers should avoid". bloodroot is a popular red natural dye used by native american artists, especially among rivercane basketmakers in the southeastern united states. however, in spite of supposed curative properties and historical use by native americans as an emetic, due to its toxicity internal use is not advisable (sanguinarine has an ld50 of only 18 mg per kg body weight). scopolia carniolica known as european scopolia or henbane bell. its toxicity derives from its high levels of tropane alkaloids, particularly atropine. the quantity of atropine is the highest in the root. solanum dulcamara commonly known as bittersweet nightshade. all parts are poisonous, containing solanine and causing fatigue, paralysis, convulsions, and diarrhea. rarely fatal. solanum nigrum commonly known as black nightshade. all parts of the plant except the ripe fruit contain the toxic glycoalkaloid solanine. solanine poisoning is primarily displayed by gastrointestinal and neurological disorders. symptoms include nausea, diarrhea, vomiting, stomach cramps, burning of the throat, cardiac dysrhythmia, headache and dizziness. in more severe cases, hallucinations, loss of sensation, paralysis, fever, jaundice, dilated pupils and hypothermia can result. in large quantities, solanine poisoning can be fatal. solanum pseudocapsicum commonly known as jerusalem cherry, madeira winter cherry, and winter cherry. all parts, especially the berries, are poisonous, causing nausea and vomiting. it is occasionally fatal, especially to children. sophora secundiflora commonly known as mescal bean and texas mountain laurel. strophanthus gratus the ripe seeds of this african plant contain ouabain, a potent cardiac glycoside that, when sufficiently concentrated, can induce cardiac arrest by binding to and inhibiting the action of the sodium-potassium pump and thereby drastically slowing the contraction of cardiac muscle cells. it was once used medicinally in small doses to treat congestive heart failure and other heart conditions, but has largely been replaced by the structurally related digoxin. extracts from strophanthus gratus and the bark of acokanthera species have long been used by somali tribesmen to poison hunting arrows; if the concentration is high enough, an arrow poisoned with ouabain can kill an adult hippopotamus. strychnos nux-vomica commonly known as the strychnine tree. the seeds usually contain about 1.5% strychnine, an extremely bitter and deadly alkaloid. this substance throws a human into intense muscle convulsions and usually kills within three hours. the bark of the tree may also contain brucine, another dangerous chemical. taxus baccata commonly known as english yew, common yew, and graveyard tree. nearly all parts contain toxic taxanes (except the red, fleshy, and slightly sweet aril surrounding the toxic seeds). the seeds themselves are particularly toxic if chewed. several people have committed suicide by ingesting leaves and seeds, including catuvolcus, king of a tribe in what is now belgium. toxicodendron spp. several species, including toxicodendron radicans (commonly known as poison ivy), toxicodendron diversilobum (commonly known as poison-oak), and toxicodendron vernix (commonly known as poison sumac). all parts of these plants contain a highly irritating oil with urushiol. skin reactions can include blisters and rashes. the oil spreads readily to clothes and back again, and has a very long life. infections can follow scratching. despite the common names, urushiol is not a poison but an allergen, and because of this it will not affect certain people. the smoke of burning poison ivy can cause reactions in the lungs, and can be fatal. the allergic reaction caused by contact with poison ivy affects more than 70% of the human population, with as many as 350,000 cases reported annually in the united states alone urtica ferox commonly known as ongaonga. even the lightest touch can result in a painful sting that lasts several days. veratrum spp. commonly known as false hellebore and corn lily. several species, containing highly toxic steroidal alkaloids (e.g. veratridine) that activate sodium ion channels and cause rapid cardiac failure and death if ingested. all parts of the plant are poisonous, with the root and rhizomes being the most toxic. symptoms typically occur between 30 minutes and 4 hours after ingestion and include nausea and vomiting, abdominal pain, numbness, headache, sweating, muscle weakness, bradycardia, hypotension, cardiac arrhythmia, and seizures. treatment for poisoning includes gastrointestinal decontamination with activated charcoal followed by supportive care including fluid replacement, antiemetics for persistent nausea and vomiting, atropine for treatment of bradycardia, and vasopressors for the treatment of hypotension. native americans used the juice pressed from the roots to poison arrows before combat. the dried powdered root of this plant was also used as an insecticide. the plants' teratogenic properties and ability to induce severe birth defects were well known to native americans, although they also used minute amounts of the winter-harvested root (combined with salvia dorii to potentiate its effects and reduce the toxicity of the herb) to treat cancerous tumors. the toxic steroidal alkaloids are produced only when the plants are in active growth, so herbalists and native americans who used this plant for medicinal purposes harvested the roots during the winter months when the levels of toxic constituents were at their lowest. the roots of v. nigrum and v. schindleri have been used in chinese herbalism (where plants of this genus are known as "li lu" (藜蘆). li lu is used internally as a powerful emetic of last resort, and topically to kill external parasites, treat tinea and scabies, and stop itching. however some herbalists refuse to prescribe li lu internally, citing the extreme difficulty in preparing a safe and effective dosage, and that death has occurred at a dosage of 0.6 grams. during the 1930s veratrum extracts were investigated in the treatment of high blood pressure in humans. however patients often had side effects due to the narrow therapeutic index of these products. due to its toxicity, the use of veratrum as a treatment for high blood pressure in humans was discontinued. vernicia fordii known as the tung tree. it is poisonous in all of its parts, including the fruit and the seeds, although some parts of the tree have been used for medicinal purposes in the past. according to one university website, just one seed from the fruit can be fatal, and other symptoms may include vomiting, diarrhea, and slowed breathing. the leaves can also give a rash similar to that from poison ivy. viscum spp. commonly known as european mistletoe; see also the related genus phoradendron. mistletoe is a common hemiparasite of trees and shrubs. toxicity varies by species, but all parts of the plant, especially the leaves and berries, contain an array of toxic chemicals, including several different viscotoxins, the alkaloid tyramine, and a