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Poisonous Plants: When They Are a Threat to Children

1997; American Academy of Pediatrics; Volume: 18; Issue: 5 Linguagem: Inglês

10.1542/pir.18.5.162

1529-7233

Ruth A. Lawrence,

Complementary and Alternative Medicine Studies

Plant ingestions among children in the United States are common.National data compiled from poison information centers across the country suggest that 5% to 10% of calls are about plant exposures and that most of these involve children younger than 6 years of age. A surprising number of ingestions occur in children 12 months and younger because of the proximity of household plants to their highchairs and playpens or because berries and leaves have dropped to the floor. Group exposures occur when older children explore their environment and eat berries because they look good or because of peer pressure. The clinical effects of the ingestions on the child can range from mildly irritating to nearly fatal, depending on the plant and the dose. The key to the problem, as with any exposure, is prevention. Knowledge about the proper identification and edibility of plants is paramount.It is not possible to compile a complete list of hazardous plants, in large part because some plants have both edible and toxic parts, such as the potato (sprouts and vine are toxic), tomato (roots and vine are toxic),rhubarb (leaves are toxic), asparagus (all but the tender shoots are toxic),and poke weed (only the early shoots are safe). The entire plant kingdom can be divided into those species that are totally safe, those that cause contact dermatitis, those that cause mechanical injury (thorns, barbs), and those that contain true toxins. One usually thinks of plants in relationship to ingestions—edible, inedible (ie, no nutritive value or taste), and toxic.Clinicians have approached the problem by trying to simplify and generalize; botanists, on the other hand, have identified and classified vegetation in great detail. The latter approach leads to accurate identification, but it is difficult to translate this information into useful data for the clinician confronted with a child who has ingested a handful of berries. Much misinformation has prevailed because of misidentification, making analysis of large numbers of exposures reported by telephone difficult to interpret. This results in the assumption that some known toxic plants are innocuous, based on reports of minimal exposure or misidentification and a lack of reported symptoms observed in these circumstances.Plants are the mainstay of an agrarian society, and our pioneer fore-fathers confronted many challenges as they foraged in a new land where the poisonous nature of the plants was unknown. Many poisonings involved large numbers of people. The best known of these outbreaks was the “milk sickness,” reported in the northeast and midwest,due to snakeroot. Cattle eating the plant, especially in times of draught,excreted its toxins into the milk. The mother of Abraham Lincoln was a victim of such a fatal poisoning. More recently, a newborn in upstate New York in the 1960s was hospitalized twice with renal failure. It was noted that the infant’s feedings were exclusively from the milk of the family’s few cows, which led to the identification of snakeroot in their fields by the Finger Lakes Regional Poison Center botanist. Use of canned milk formula prevented further episodes. The risk of snakeroot poisoning today is minimal,not only because of the availability of commercially prepared animal feed in times of drought but because commercially available milk is pooled from thousands of cows, and any toxin in the milk of a few is greatly diluted.The text Poisonous Plants of the United States and Canada by John M. Kingsbury is the landmark publication used by poison centers throughout North America for decades. The author points out the difficulties in documenting botanical toxins because so many undocumented reports have been reiterated in published writings. Dioscorides’ manuscript“ Of Medicinal Matters” represents the pre-eminent compilation of supposed active properties of plants prior to the first century AD. Many centuries lapsed before further documentation appeared. The printed herbal appeared in 1470, and its era lasted two centuries. Most of the work on plant toxins prior to the 20th century was published in German and involved the use of plants as medicinals. The inception of chemistry as a science in the United States can be traced to the arrival of Priestley in 1794. The investigation and experimental approach to plant chemistry began in the early 1880s. In 1887,the Hatch Act was passed, providing federal funds for agricultural experimentation. Federal investigations of poison as it affected agricultural animals was a prime focus following the development of the Bureau of Plant Industry in 1905. Even today, the scientific study of plant toxins is almost exclusively in veterinary medicine, with occasional reports of serious exposures in humans. Most of the cases never are reported in the literature.The objectives of this article are to increase awareness of potential hazards of toxic plants, to aid in identifying informational resources, and to assist the pediatrician in recognizing symptoms of exposure and providing appropriate treatment. Plants known to be dangerous should be given the same respect as other household hazards. Parents and children should be educated never to ingest an unidentified plant in the house, yard, or the wild. This discussion will not include mushrooms, although they represent an increasing number of life-threatening exposures, as more immigrants hunt for wild mushrooms that resemble edible ones from their homelands.The dilemmas of identification are multiple. Families rarely know what the plant is, and if they do offer a name, it is the trivial or common name such as dumb cane, mother-in-law’s tongue, or elephant’s ear, all of which, by usual definition, are members of the Araceae family. However, these common terms may refer to different plants in different regions of the country. For example, spider plant in the East refers to a hanging house plant, whereas it refers to an outdoor ground cover in parts of the West. In the yard or woods, vines that have berries may become entangled with other vines, bushes, or trees, increasing the chance of misidentification if a poisonous berry dangles from a nontoxic bush. This is particularly true of nightshade, an incredibly hardy and tenacious plant whose berries survive into the winter and that almost always entwines another plant. The growing numbers of house plants found in the average home increases the risk of access, even to the youngest children. Most people recognize philodendron with its heart-shaped leaves alternating on a vine. These plants, which are in the arum family of Araceae, contain needle-like crystals (raphides) of calcium oxalate and the protein asparagine, which are very irritating to the mucous membranes if bitten or chewed. A new young plant contains less toxin volume-for-volume than a large old dark green leaf. Berries from household flora such as holly, Jerusalem cherry, mistletoe, bittersweet, and peace lily are toxic. Another source of potentially toxic vegetation from the competitive florist market is the many imported exotic plants from around the world. The average household contains several unidentified plants; consumers should be encouraged to learn the proper names of the plants they purchase.The increasing interest in herbs and herbal medicines poses an additional challenge because there are no regulations to control their distribution and sale. They often are not labeled; if they are, it is with a trivial name of no botanic significance. Although many are safe, some herbal teas contain comfrey leaves (Symphytum)or thread-leafed groundsel (Senecio longilobus), which contain hepatotoxic pyrropizidine alkaloids known to cause hepatotoxicity and veno-occlusive disease. Other teas have warfarin-like properties. Many of these teas have been banned in other countries. When taking a history, it is imperative to ask specific questions about the use of herbal teas, foods, and medicines.Telephone descriptions of the offending plant may be misleading unless the plant has some special characteristic that even a casual observer can see, such as the fruit of the yew (taxus). The ripe fruit is bright red and oval and has a round hole in the end so that the green (toxic) seed is readily visible. The plant is an evergreen bush or tree that has flat needles. All parts of the yew are toxic, but the green seed is most toxic. The red flesh of the fruit is sweet, and in small amounts, nontoxic. A handful of the fruit could cause symptoms even if the seeds are discarded. The toxin is taxine, a cardioglucoside.Poison centers have access to multiple reference books, as well as the Poisondex computer data base, and usually qualified local plant and weed botanists who know the regional vegetation can assist in identification. A special dedicated data base,ToxPlant, allows poison center staff to make accurate identifications. This system has a computer-assisted algorithm for the identification process,even if only a few obvious characteristics are known about the plant, such as leaf shape, size, and placement on the stem. The simplest and most reliable resource when a child is reported to have been exposed to a possibly toxic plant is the regional poison center.It is difficult to determine how much of a toxic plant can cause poisoning. Unless children were under constant observation, it may be impossible to ascertain how many berries were ingested. Even among children who ordinarily are truthful, the number of berries they say they ate rarely coincides with what is found in the vomitus, sometimes by a factor of 10 even in 8- to 12-year-olds. Further,not all berries, leaves, or roots of the same classification contain the same amount of toxin. This fact has been demonstrated by experience with the drug culture since the 1960s. At that time, a popular pastime was to gnaw on morning glory seeds for their psychedelic effect, but violent reactions similar to that of a strong dose of lysergic acid diethylamide (LSD) have been reported from the same number of seeds as had produced only a mild high in previous instances.The recommendations as to degree of toxicity usually depend on the size of the victim and the presumed exposure estimated from examining the mouth, teeth, and hands of the victim; the condition of the plant; and the length of time the child was unattended. A single berry or bite of leaf smaller than a half dollar of most plants is considered to be mildly toxic; it is safe to watch for symptoms at home. Depending on the toxin and the poison potential, larger ingestions would be treated by removal from the stomach, a dose of activated charcoal, or both. The most difficult decision rests with the estimation of the quantity of ingestion in small children. Evidence that birds or animals eat the plant without symptoms is no guarantee that it is safe for humans; humans do not tolerate more than a few blades of ordinary grass, yet many animals, especially ruminants, depend on grass for survival.To reduce morbidity from plant exposures, pediatricians should: Exposure to potentially hazardous plants may occur by ingestion,skin contact, inhalation of pollens, and mechanical injury due to barbs,thorns, and minute stinging hairs (nettles). This discussion will focus on ingestion and contact reactions.Numerous plants cause dermatitis, but the average person rarely is in contact with them. Similar to other allergies, the reaction depends on previous sensitization of the individual. The seriousness of the skin reaction depends on the plant contacted, the degree of contact, and the susceptibility of the individual.The best known of this group is the Toxicodendron species, which includes poison oak, ivy, and sumac, all of which contain a sap that is the offending substance and is found in all parts of the plants.Poison ivy (Rhus radicans) is found throughout Canada and the United States along rivers,lake shores, and the edges of woods, streams, fences, and even buildings. It can be a woody shrub or a vine climbing along the ground or high in trees or poles. The sentinel finding is alternating, shiny three leaflets. Whitish flowers and fruits hang in a nonhairy drupe. The jingle “Leaves of three,quickly flee; berries white, poisonous sight” should be heeded!Poison oak (Rhus toxicodendron) is a low shrub found in sandy soil, dry barrens, or pine woods in restricted geographic areas of New Jersey, Maryland, Missouri,Tennessee, south to Florida, and Texas. It also has three leaflets whose undersides are hairy, as are its yellowish flowers and fruit.Poison sumac (Rhus vernix) is a shrub 5 to 8 ft tall or a small tree that has smooth grey bark and pinnate leaves that alternate between 7 and 11 leaflets. The stalks are reddish, and fruits hang in cream-yellow hairless drupes.All of these plants cause itching, burning, redness, and small blisters that develop within a few hours or up to 5 days following exposure. The skin reaction can be caused by or contacted from contaminated clothes, animals,or objects or even from burning brush in very sensitive individuals.In case of contact, immediate washing with strong soap to remove the plant oil or sap is imperative. The pediatrician may be contacted when large blisters and local swelling develop.The prime goals of treatment at this stage are to protect the skin, prevent infection, relieve the itching, and prevent the excoriation associated with uncontrollable scratching. Most creams are relatively ineffective; those containing antihistaminics should be avoided. Calamine lotion may facilitate the drying process. Local application of corticosteroid creams usually helps relieve itching and swelling. Oral antihistaminics can be prescribed; a dose at bedtime will reduce nighttime scratching. When large areas of the skin are involved, especially around face and eyes, systemic steroids may reduce swelling and itching and hasten healing.Trumpet creeper or cowitch (Campsis radicans) is a common woody vine in the eastern states that covers trees, poles, and fences. These leaves are pinnately divided into 9 to 11 ovate leaflets that have jagged edges. Its characteristic flowers are orange to red five-lobed trumpets 2 to 3 in long. The fruit is in a long slender capsule with many winged seeds. Contact with leaves or flowers causes inflammation and blisters that last for several days. Treatment is symptomatic.Other common skin sensitivities are to poinsetta (milky juice; Euphorbia sp),ragweed, cashew nut (shell or oil), asparagus, papaya, chrysanthemum, lime(skin or thorns), Jimson weed, larkspur, bleeding heart, fig tree (sap),English ivy, iris (rhizomes), oleander, primrose, buttercup, and the bulbs of tulips. The group of stinging nettles includes several varieties (Urtica diocia, Hesperocnide sp, and Laportea canadensis).Giant hogweed (Heracleum mantegazziarium) was imported to the United States for use as borders for fields or a hedge along the road. It is a perennial herb that grows to 15 ft, with leaves 3 ft long, alter-nating and clasping the stem. The leaves appear in groups of three and have large toothed edges. The white flower is 4 ft in diameter. The hollow stems are used by children for peashooters, popguns, and whistles, and the vegetation makes an alluring fort or hiding place. The sap causes severe blistering and painful rash, which may lead to brown discoloration and scarring. Symptoms differ from those of other contact dermatitis because the redness and burning develop promptly with light exposure, but the intense residual redness may persist for months. The rash is photosensitive, is intensified by exposure to sunlight, and may recur for weeks or months on exposure to ultraviolet rays.Treatment is symptomatic and similar to that for poison ivy. Cool compresses may relieve the burning. Because of the role of ultraviolet light,the affected area should be shielded from sunlight for a protracted period of time.Other plants that cause phyto-photodermatitis are wild parsnip(Pastinaca sativa) and gas plant (Dictamnus albus).The Arum species includes the family Araceae. These stemless plants have 8- to 10-in leaves, tuberous roots, showy flowers, and brilliant red fruit. The toxin is calcium oxalate raphides and a proteinaceous liquid,asparagine. The toxic effect following ingestion is burning and irritation,with edema of the lips, mouth, tongue, pharynx, and stomach. There may be nausea, vomiting, or diarrhea. The pain and swelling usually will respond to fresh or bottled lime juice. Cool liquids (ice cream, popsicles) may give some relief, especially in children. There is some risk of laryngeal edema when large mature stems are bitten, thus the name dumbcane for dieffenbachia. Other house plants that have similar effects are philodendron, alocasia,colocasia (elephant ears), caladium, and peace lily (Fig.1) F1.Although most berries and fruits are edible, a significant number are toxic. The following discussion will cover only a few of the best known, most readily available ones that are toxic. Their characteristics are sufficiently distinct for easy identification,even by telephone description. The clinician is encouraged to be familiar with the most common ones in his or her locale.Pokeweed (Fig. 2) is known by many common names—pokeberry, inkberry, red weed, scoke, and pigeon-berry, to list just a few. The large perennial root stalk is most toxic and has been confused with parsnip and horseradish, which are edible. The stout purplish stalks may grow to 12 ft. The flowers are small and greenish white on a short stalk. The berries are succulent deep purple, almost black, and are attached by a short red stem. When the berries are ripe, the stalks usually are red—a very distinguishing characteristic. The juice looks like purple ink.The most toxic part of the plant is the root, but the leaves and unripe berries also are toxic. The toxin is phytolaccatoxin and related triterpenes. After a delay of 2 to 3 hours, ingestion causes nausea,persistent vomiting, intense cramping, and later diarrhea, often persisting for 48 hours and resulting in severe dehydration.The management is to remove the material immediately from the stomach. However, because symptoms often are delayed and the problem is not recognized for several hours,administration of activated charcoal may be necessary. If intense vomiting has begun, the only treatment is supportive, replacing fluid loss and relieving abdominal pain.Purple nightshade (Fig. 2) is the common variety in the United States. As a member of the Solanum sp, it is related to the potato and Jerusalem cherry (S dulcamara). It is a woody vine or shrub that has small purple flowers with five petals and a pointed yellow stamen. The berries are red when ripe and hang in a drupe. When crushed, they smell like rotten potatoes. The leaves can be oval or heart-shaped. A conspicuous feature is the presence of flowers at the same time as green and ripe red berries.Children are particularly sensitive to the toxin, experiencing gastric irritation, scratchy throat, fever, and sometimes diarrhea. The atropine-like symptoms along with dilated pupils, flushed appearance, and bizarre behavior are particularly common and persist for hours to days. Fluid replacement may be required.When ingestion of the red berries is suspected, activated charcoal is appropriate immediate treatment. Further treatment is supportive, pending the development of symptoms. The ingestion of the black berries of deadly nightshade necessitates aggressive treatment with lavage, charcoal, and medical observation. Deaths are reported in the literature from respiratory depression following large ingestions by children.This plant, also known as burning bush and strawberry bush, has been cultivated in North America and originates as a vine or small bush that responds well to training and trimming. The very shiny dark green leaves are almost stemless (Fig. 2). The tiny flowers are purple-green, and the fruit has a beige capsule that splits open to reveal a bright orange to red aril. The leaves and the fruit persist through the winter. E europheses is known for its toxin, evomonoside, a digitalis-like cardio-active glucoside. The symptoms reported are watery diarrhea delayed for 10 to 12 hours and persistent emesis. Fever, hallucinations, and somnolence have been reported. Early treatment is administration of activated charcoal. Later treatment is symptomatic, with emphasis on fluid replacement. The unique characteristics of this plant are the evergreen leaves that endure the winter and a fruit that resembles the parasitic vine of the oak tree, also known as bittersweet.The yew are evergreen trees and shrubs that have alternate branchlets and reddish brown thin-scaled bark; the flat needle-like leaves are paired on the twig. The hard green seeds are covered by a bright red fleshy cup open at the top (Fig. 2). All parts contain the poisonous alkaloid taxine. Ingestion causes vomiting and diarrhea, dry mouth,dilated pupils, jitteriness, muscle weakness,and breathing difficulties. In severe cases, brachycardia and arrythmias have been described.Management is the administration of activated charcoal (emesis may be induced if ingestion is discovered immediately). Symptomatic treatment is indicated; electrocardiographic monitoring is required if any symptoms develop. Anaphylactoid reactions have been reported and require administration of epinephrine and corticosteroids.The classic defining characteristic of the fruit is the hole in the flesh that reveals the large seed. Although one or two of the fruit can be eaten if the seed is discarded without puncturing it, symptoms have been reported(dizziness and lightheadedness) in adults who have eaten 10 to 12 at one time. Yew is very toxic to foraging animals, killing cows, goats, and deer that ingest large amounts.Pods hold special attraction for children, particularly in the fall and winter when other plants have withered away and the pods continue to dangle within reach. Three such examples are wisteria, milkweed, and black locust(Fig. 3). Others are members of the pea family—Fabaceae or Leguminosae, many of which are not only edible but familiar and important parts of vegetable crops. Within this same family, however, are some of the most dangerous of poisonous plants. Jequirity bean or rosary pea from the tropics, golden chain tree, wild sweet pea, and Kentucky coffee tree are examples.These woody vines produce spectacular cascades of sweetpea-like blue flowers (pink and white varieties also exist). The formed pods are smooth in some varieties and velvety in others, but all are hardy through the winter. The entire plant is toxic, including the flowers,and contains an uncharacterized glycoside, wistarine. Two seeds are sufficient to cause serious symptoms in a child. The major symptoms are intractable vomiting and abdominal pain. Although diarrhea is minimal, the total fluid loss may hypovolemic shock. If discovered immediately, treatment is emesis and activated charcoal. If spontaneous vomiting has begun, fluid management is essential.Milkweed has an attractive pod that often is collected by children. Its common name stems from the abundant white milky sap that flows from all parts, including the roots, which has been used to cure warts and initiate vomiting. There is a woody stalk, and dark waxy green leathery leaves 4 to 5 in long oppose each other on the stalk. The flowers are small,purple, and funnel-shaped. The fruit develops in a long and narrow pod, with soft and silky stands and small seeds. The pods often are included in dried foliage arrangements. The milk sap contains glycosides, including aesclepiaclin, resins, and volatile oils. Symptoms from ingestion include diaphoresis, increased secretions, vomiting, and diarrhea. Extracts of the leaves or roots cause similar symptoms. Folklore suggests that the tender shoots be eaten if they are boiled in several waters. Cattle develop similar symptoms when they graze the plants. Treatment for ingestion is symptomatic. Syrup of ipecac is not indicated; charcoal is indicated only if more than one pod was ingested.The black locust is a large tree often growing to 80 ft. The compound leaves have 7 to 19 elliptical leaflets with smooth edges. A distinguishing feature is a pair of woody thorns on the branch where the leaf stem emerges. The creamy white, fragrant flowers cascade in clusters. The fruit is a flat reddish-brown pod 4 in long containing four or five black seeds. The bark,seeds, and leaves are toxic. Children usually select the seeds to eat,although cases of poisoning have been reported from sucking the twigs.The toxin is robin, a plant lectin (toxalbumin) that interferes with protein synthesis in the small intestine. A latent period of several hours usually follows ingestion. Nausea, vomiting, and diarrhea develop. Other symptoms are the result of hypovolemia and fluid loss. Management is symptomatic,with correction of fluid loss. Activated charcoal can be effective if administered before symptoms begin.Plants toxic to humans abound in home and yard as well as open fields and woods. Only experienced botanists and serious students of edible vegetation can distinguish safely what is edible, inedible, or simply toxic. Parents should be instructed to protect their children from truly toxic household plants and train their children never to eat a plant not provided to them by someone trustworthy as edible.If a child or an adult consumes a possibly toxic plant, the regional poison center should be contacted for identification and management instructions. As with all potential poisonings, the sooner the management is initiated, the better the outcome. Adults have been seriously poisoned by confusing a toxic plant with something that they thought was edible(eg, pokeweed root for horseradish).The pediatrician’s office should be a model, with only nontoxic plants on display—no dieffenbachia, peace lily,pothos, or philodendron, for example.