The holiday season is in full swing and with it comes the festive decorating and bringing some of the holiday’s traditional plants into the home for gatherings among family and friends. With all of the hustle and bustle of young children and pets bounding about, one must still be careful of children and pets around holiday plants. Some of the traditional holiday plants may contain potentially toxic substances that could cause significant adverse effects to a toddler or dog that absently begins chewing on the leaves. Here are some holiday plants that may cause a safety concern when consumed by either small children or pets, as well as others once considered highly poisonous, but in reality, are rather innocuous.
People may not realize it, but the bulb and leaves of the amaryllis (species from the Amaryllis or Hippeastrum genera) plant are quite toxic, containing the pheanthradine alkaloid lycorine,1,2 which can act on neurokinin-1 receptors, and potential absorption from chewing on the leaves could induce nausea and vomiting that can last for several hours.3 Other more intense effects (with increasing levels of intake) include tremors, hypotension, seizures and sedation. The Kalanchoe plant (the genus contains approximately 125 species) is a recent addition to the Christmas holiday, found to be able to be forced into bloom during the winter. Dwarf varieties are used as houseplants year around. However, Kalanchoe is a cardiotoxic plant, containing bufadienolides in all parts of the plant, but the highest concentrations are found in the flowers.4 Bufadienolides inhibit the sodium-potassium adenosine triphosphatase enzyme in the myocardial cell membrane, resulting in a loss of normal myocardial electrical function. Dogs seem to be especially sensitive to the cardiotoxic effects of the cardiac glycosides contained in the Kalanchoe plant, even exhibiting toxicity from consumption of livers from goats fed Kalanchoe leaves.5 The lily of the valley (Convallaria majalis) contains digitalis glycosides that can reach toxic levels from excess plant intake,6 shown to be highly toxic to cats.7
One holiday houseplant has been on the top of most lists of poisonous plants: the poinsettia (Euphorbia pulcherrima). The upper leaves are typically red or white, resembling a flower, and are frequently used as a living decoration. While all Euphorbia plants produce a milky-white sap that is irritating and similar to latex, the diterpeniod euphorbol esters and steroids with saponin-like effects in the sap are the “toxic” components that have a soap-like effect on skin and mucous tissues. The ingestion of the sap mainly causes irritative effects, resulting in enhanced salivation, vomiting, and diarrhea. These effects are not as toxic as was once thought, resulting in a greater concern for consumption of the poinsettia than is actually warranted.8 In the same manner, another favorite holiday plant is the Christmas cactus (Schlumbergera truncata), which can be forced to bloom during the winter months. The leaves may contain sharp needles that are highly irritating to the mouth and stomach when consumed, but in general the Christmas cactus is considered to be non-toxic, with ingestion resulting in mild vomiting, diarrhea and nausea.8 Like the poinsettia and Christmas cactus, the berries of the holly plant (Ilex aquifolium) contain saponins, p-hydroxybenzoic acid, ursolic and oleanolic acids and theobromine (similar in effect to caffeine) that can be somewhat toxic to young children. Consumption of the holly berries can cause mild gastrointestinal irritation, vomiting and diarrhea, but the effects have typically been found to be rather mild when only a small number of the berries were consumed.
The holiday season is filled with family and friends gathering together for food and fun, but make sure that young children and pets have limited access to those plants that could cause toxic effects when ingested.
References:
Kretzing, S., Abraham, G., Seiwert, B., Ungemach, F.R., Krügel, U., Teichert, J., Regenthal, R. (2011). In vivo assessment of antiemetic drugs and mechanism of lycorine-induced nausea and emesis. Arch Toxicology. 85(12):1565-73. doi: 10.1007/s00204-011-0719-9.
de Andrade, J.P., Pigni, N.B., Torras-Claveria, L., Guo, Y., Berkov, S., Reyes-Chilpa, R., el Amrani, A., Zuanazzi, J.A.S., Codina, C., Viladomat, F., and Bastida, J. (2012). Alkaloids from the Hippeastrum genus: Chemistry and biological activity. Rev. Latinoamer. Quím. 40/2(2012): 83-98.
Kretzing, S., Abraham, G., Seiwert, B., Ungemach, F.R., Krügel, U., Regenthal, R. (2011). Dose-dependent emetic effects of the Amaryllidaceous alkaloid lycorine in beagle dogs. Toxicon. 57(1):117-24. doi: 10.1016/j.toxicon.2010.10.012.
McKenzie, R.A., Franke, F.P., Dunster, P.J. (1987). The toxicity to cattle and bufadienolide content of six Bryophyllum species. Aust Vet J. 1987 Oct;64(10):298-301.
Botha, C. (2016). Potential Health Risks Posed by Plant-Derived Cumulative Neurotoxic Bufadienolides in South Africa. Molecules. 16;21(3):348. doi: 10.3390/molecules21030348.
Bara, V. (2001). Digoxin overdose: clinical features and management. Emerg Nurse. 1;9(3):16-21.
Fitzgerald, K.T. (2010). Lily toxicity in the cat. Top Companion Anim Med. 2010 Nov;25(4):213-7. doi: 10.1053/j.tcam.2010.09.006.
Evans, Z.N. and Stellpflug, S.J. (2012). Review: Holiday Plants with Toxic Misconceptions. West J Emerg Med. 13(6):538-542.