BOTANY IV
Kate F a r t h i n g , P h a r m D
Poisonous Plants
Understanding the Need for Accurate
Identification and Timely Information
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The intent of this article is to review commonly
ABSTRACT Only a few of the thousands of existing plants encountered poisonous plants and to suggest
are considered to be poisonous or potentially harmful in any resources for information when exposure to a poiso-
manner. No universal guidelines are available to determine nous plant occurs.
whether a plant or specific exposure will result in harm. This
Sources of Poisonous Plants
article reviews commonly encountered poisonous plants and The Home and the Workplace
suggests resources for information if exposure occurs. The most commonly reported plant exposures are
Poisonous plants are commonplace in homes or offices and the ingestion of household plants by children.
should be properly identified in anticipation of a child or ani-When any plant is ingested, it is important for the
mal ingesting one of these plants. Although plants or mush- health care worker to know how much and what
parts of the plant have been ingested. The harmful
rooms encountered in nature may resemble common foods, effects of a plant vary with geographic location, sea-
one should ask an expert to positively identify them before son, and stage of growth.5
eating them. The telephone number of a regional poison con- Two popular houseplants, the dieffenbachia
trol center or another emergency contact should be posted in (dumbcane) (Fig 1) and philodendron, members of
an accessible area in case of an accidental poisoning. This is the arum family, contain6 calcium oxalate crystals in
their stems and leaves. Chewing releases the sap,
the fourth and final article in a continuing education update which can come in contact with the mouth, hands,
series. Following this series, particpants should be able to rec-
or eyes, causing irritation, burning, and swelling.
ognize the hazards and know what to do when encountering The irritation generally lasts several hours, and
a poisonous plant or mushroom, understand how plants can mouth and throat involvement is particularly
bothersome. Treatment at home, on the recommen-
clean the environment, and identify the role plants play in
dation of qualified medical personnel, consists of
ancient and modern-day pharmaceuticals. thoroughly washing the hands and face with soap
From Drug Use Only a small number of the thousands of existing and water, and giving milk or ice cream to soothe
Management and plants are considered poisonous or potentially the irritated mouth or throat.3 If the patient experi-
Information harmful in any manner.1 Unfortunately, no uni- ences difficulty in breathing or excessive swelling of
Services, Oregon the mouth or tongue, he or she should be referred to
versal guidelines are available to help determine
Health Sciences
whether a plant or specific exposure will result a physician immediately. No specific laboratory tests
University, Portland,
Ore. in harm. are available to identify calcium oxalate toxicity.
Reprint requests to In a 1993 study by the American Association of Although the dieffenbachia and philodendron are
Dr Farthing, Oregon Poison Control Centers, plants were the fifth most probably the most widely known plants associated
Health Sciences common substance involved in exposure to with calcium oxalate toxicity, caladiums (angel's
University, Drug Use
humans. Plant accounted for 94,725 of the wings), calla lilies, alocasia (giant elephant's ears),
Management and
Information 1,751,476 human exposures reported in 1993.2 Of and anthuriums (tail flowers) also are members of
Services, 3181 SW these exposures, 7,178 cases were referred to a the arum family that contain sharp calcium oxalate
Sam Jackson Park health care facility for treatment, and only one crystals in their leaves and stems.3
Rd, OP24, Portland,
case resulted in death. The true incidence of expo- During the holiday season, the popularity of cer-
OR 97201; or e-mail:
farthing@ohsu.edu
sure is suspected to be larger, however, because tain household plants increases as does the potential
many instances of poisoning are not reported to for ingestion. Mistletoe berries can cause abdominal
poison control centers or documented.2'3
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pain and diarrhea, even if only a few berries are
eaten. Consumption of large quantities of the
berries or of tea made from the leaves can result
in severe stomach irritation. 1 ' 3 The poinsettia
leaves and stem contain a milky substance that
can irritate the skin, although only minor stom-
ach upset usually is observed with ingestion.3 No
specific laboratory tests are available to identify
toxicity from mistletoe or poinsettia.
Outdoors
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Poison ivy, poison oak, and poison sumac con-
tain a highly irritating substance, urushiol, which
is found in all parts of the plant. People sensitive
Fig 1. The dieffenbachia (dumbcane) contains calcium oxalate crystals in its a-
to this substance experience irritation as soon as
stems and leaves. The sap can cause irritation, burning, and swelling to the |
their skin comes in contact with these plants. mouth, hands, or eyes. 5
Even the smoke produced when burning the
plants or clothing that has come in contact with
the plants can result in symptoms. An itchy skin
rash and blisters appear on exposed areas within
hours (up to 5 days) after contact with urushiol,
and generally last 2 to 3 weeks. After a person has
been exposed, he or she should remove and laun-
der contaminated clothing, and wash all exposed
areas of skin with soap and water. Topical or oral
antihistamines may ease the itching sensation. No
specific laboratory tests are available to identify
urushiol toxicity.
Flowering plants that contain cardiac glyco-
sides, which directly affect the heart, include ole-
ander (Fig 2), foxglove, and lily of the valley. All
parts of these plants are potentially toxic, and
symptoms of exposure include nausea, vomiting, Fig 2. The Neureum oleandar contains cardiac glycosides, which directly affect
diarrhea, abdominal cramps, headache, slowing the heart. The plant, though beautiful to look at, is potentially toxic, with symp-
of the heart, and irregular heartbeat. Ingestion of toms including nausea, vomiting, diarrhea, abdominal cramps, headache,
cardiac glycosides can lead to convulsions and slowing of the heart, and irregular heartbeat.
cardiac arrest. The toxicity associated with the
cardiac glycosides sometimes can be detected by
older, nonspecific assays, but not with specific
digoxin immunoassays (Baer, DM. October 1995,
personal communication), and the patient's
o c
metabolic status should be followed closely. 0
Some of the most serious toxicities occur
when people collect and eat unfamiliar plants
and mushrooms from the wild. A few mushroom
varieties are highly toxic, and the person collect-
ing mushrooms for eating should know the exact
identity of the mushroom. 3 Depending on the
type of mushroom ingested, symptoms can range
from nausea, vomiting, diarrhea, and abdominal
cramps to drowsiness and hallucinations. Anyone
experiencing symptoms after eating mushrooms
should be treated immediately. If possible, the Fig 3. Poison hemlock (Conium maculatum) can be mistaken for a wild carrot
affected person should bring a sample of the (also known as Queen Anne's lace) and its leaves mistaken for parsley. Toxicity
mushroom to the treatment facility so that its with this plant involves central nervous system stimulation followed by severe
identity can be confirmed. central nervous system depression.
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CHEMICAL CATEGORIES OF POISONOUS PLANTS
Chemical Category/Characteristics Common Plant Names Comments
Alkaloids Belladonna, jimsonweed, Alkaloids represent a category of
Alkaloid molecules usually have a hemlock, tobacco, poppy, ergot, significant research in medicine
ringlike structure and contain nightshade, larkspur, star-of- and human toxicology. They usu-
nitrogen. They are generally Bethlehem, yew, coffee ally are found throughout all parts
thought to produce psychoactive of the plant and can be hazardous
symptoms. The alkaloid content of to livestock.
plants usually does not vary with
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changing ecologic conditions.
Glycosides Cyanogenic glycosides: Cyanogenic glycosides:
Glycosides vary greatly in hyangea, flax, elderberry, wild Hydrocyanic acid is produced on
structure, but all contain at least a cherry, amygdalin (found in hydrolysis of glycoside, and
simple sugar molecule and pits or seeds of wild cherry, cyanide toxicity can result.
something that is not a sugar. The peach, apple, apricot and Steroid glycosides:
glycoside content of a plant almond) Cardiac glycosides:
depends on both intrinsic Steroid glycosides: They are commonly used in
(genetics, age) and extrinsic Cardiac glycosides: medicine to strengthen the
(climate, moisture) factors. foxglove, lily of the valley, heart muscle.
oleander Saponins:
Saponins: Ingestion can cause gastric
corn cockle, English ivy, irritation.
alfalfa, pokeweed Coumarin glycosides:
Coumarin glycosides: Under wet conditions, sweet
Ohio buckeye, sweet clover clover can spoil, causing
bleeding in livestock.
Oxalates Soluble oxalates: Soluble oxalates:
Oxalic acid is irritating to tissues beet, sorrel, rhubarb, Russian Ingestion can result in a drop in
when ingested. In plants, it occurs thistle, greasewood serum calcium on absorption
in both a soluble (sodium or Insoluble oxalates: and formation of oxalate crystals
potassium oxalates) and an caladium, elephant's ear, in the kidneys.
insoluble (calcium oxalate) form. dumbcane, philodendron Insoluble oxalate crystals (calcium
oxalate):
When chewed, these crystals
produce irritation and burning.
Resins and Resinoids Urushiol, milkweed, Urushiol causes contact
Difficult to categorize in chemica marijuana, water hemlock, dermatitis (poison ivy, oak, and
terms due to diversity. Physical laurel, chinaberry tree, sumac). Marijuana has become a
properties on extraction from rhododendron popular euphoric drug when
plants are similar. smoked, and some resins of the
plant have medicinal value.
The common name hemlock refers to several be mistaken for parsley, whereas water hemlock
species of plants, some of which are highly toxic, has been mistaken for a turnip and various other
and others of which, such as the hemlock tree similar-looking edible species.3 With both plants,
(Tsuga canadensis), are harmless. Poison hem- all parts of the plant are considered toxic, but the
lock (Conium maculatum) (Fig 3) and water roots and stems have the highest concentration
hemlock (Cicuta douglasii) are easily mistaken of toxins. Symptoms of poison hemlock toxicity
for edible plants; the results of this misidentifica- are similar to nicotine poisoning and include ini-
tion may be tragic. 3,4 Young poison hemlock tial central nervous system stimulation followed
plants resemble wild carrots and the leaves can by severe central nervous system depression.
Water hemlock poisoning results in central
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nervous system stimulation and symptoms dangers in your home, especially if small children
include salivation, excessive sweating, convul- are present. The telephone number of the regional
sions, and eventual respiratory failure. The onset poison control center or another emergency con-
of symptoms after either poison or water hem- tact should be located in an accessible area in case
lock ingestion is rapid (within an hour), and of an accidental poisoning.©
treatment by medical personnel should be imme-
diate. No specific laboratory tests are available to Acknowledgment
identify either poison or water hemlock toxicity. The author wishes to thank George H. Constantine, PhD,
professor of pharmacology, Oregon State University College
Although a comprehensive discussion of all of Pharmacy, Corvallis, Ore, for providing photographs of
poisonous plants is beyond the scope of this arti- poisonous plants.
cle, a partial listing of poisonous plants is shown
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in the Table. References
1. Blackwell WH. Poisonous and Medicinal Plants.
Englewood Cliffs, NJ: Prentice Hall; 1990.
Sources of Information 2. Litovitz TL, Clark LR, Soloway RA. 1993 annual report of
Parents and guardians are cautioned to keep chil- the American association of poison control centers toxic
dren and pets away from harmful substances, exposure surveillance system. Am ] Emerg Med. 1994;
12:546-584.
which run the gamut from household cleaners 3. Turner NJ, Szczawinski AF. Common Poisonous Plants of
and medications to plants and mushrooms. North America. Portland, Ore: Timber Press; 1991.
Regardless of whether or not you have children or 4. Bernstein JN. Common plant ingestions. / Fla Med Assoc.
1994;81:745-746.
pets, you should know the identity of the plants, 5. Eisen T. Plants—general principles. Clin Tox Rev. 1989;
shrubs, and bushes growing in your yard as well 11:1-2.
as inside your home. If you are unsure of the 6. Gardner DG. Injury to the oral mucous membranes Test Time!
caused by the common houseplant, dieffenbachia. Oral Surg Look for the CE
identity of a plant, consult a friend or neighbor. Oral Med Oral Pathol. 1994;78:631-633. Update exam on
Confirm the identity with an expert, such as a Botany (601) imme-
florist or employee at a local nursery, who usually Please let us know your opinion of the diately following this
can identify plant varieties from clippings. A Botany series. article. Participants
botanist associated with a community college or will earn 4 CMLE
1. The series met the objectives stated in the
credit hours.
university is a good resource, as is the county abstract.
extension office, for help in identifying house- Deficient Excellent
1 5
hold plants and the potentially toxic plants com-
2. The series provided useful technical data or
monly found in your area. Always remove wild original ideas.
mushrooms before an exploring child finds them Deficient Excellent
in the yard. Never eat wild mushrooms without 1 5
knowing their proper identity. 3. The information provided in the series was
new and timely.
In the event of ingestion or exposure to a
Deficient Excellent
plant, contact your regional poison control cen- 1 5
ter. If you know the common or botanical name
of the plant and are able to describe the appear-
ance of the plant, the poison control center per-
4. Technical points were explained clearly and
were easy to comprehend.
Deficient Excellent
I
1 2 3 A 5
sonnel will be able to assist you more efficiently.
They will make treatment recommendations 5. The text was organized logically. ©
c
Deficient Excellent o
based on the type of plant, how much and which 1 2 3 4 5
parts of the plant have been ingested, and any 10
6. Illustrations, charts, and tables helped
symptoms you or your child or pet are experienc- explain text and added to series value.
ing after exposure. The poison control center per- Deficient Excellent
sonnel also will refer you to an emergency 1 2 3 4 5
department or to your family physician or veteri- Comments: (attach additional pages, if
necessary)
narian for follow-up if appropriate.
Conclusion
A relatively small number of plants are consid- Thank you for your input. Mail this form with
ered poisonous, but those that are poisonous can your exam or alone to:
Laboratory Medicine, 2100 W Harrison St,
cause serious consequences if ingested. If explor- Chicago, IL 60612-3798.
ing the wilderness, always know the identity of
the plant before you eat it. Know the potential
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