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Dumb cane houseplant poisonous, but unlikely to kill

Is a common houseplant deadly poisonous? According to a number of Facebook posts, exposure to the dieffenbachia plant, also known as dumb cane or mother-in-law’s tongue, can kill.

One post claims the plant is “dangerous to the point of killing a child in one minute and an adult in 15 minutes” and can cause blindness, too. “If you touch it by chance you should never bring your fingers to your eyes, as this could cause permanent blindness. Warn your friends and your family.”

The claims about dieffenbachia have been repeated multiple times on blogs, going back as far as 2009. They’ve also been shared widely on Twitter.

Should the plant be so feared? We plucked our way through the facts.

Multiple species, sap poisonous

Taxonomy websites show that there are many species of dieffenbachia plants. According to Oxford Plants 400 at Oxford University’s plant science department the genus has 25 to 50 species, while World Flora Online says there are 27 species

The toxicity of the plant is widely recorded. According to Oxford Plants 400, the plant’s sap contains calcium oxalate, which is poisonous and associated with the formation of kidney stones.

“Consequently, great care must be taken when handling dieffenbachia plants, especially over getting sap into the mouth and eyes. One response the sap provokes is swelling of the throat, resulting in speechlessness; hence the common name ‘dumb cane’,” Oxford Plants 400 warns.

Mild symptoms

Africa Check reached out to the National Capital Poison Center in Washington DC, a non-profit organisation that works to prevent injuries from poison in the US capital and surrounding towns. It is accredited by the American Association of Poison Control Centers.

Dr Lindsay Liu, a pharmacist and specialist in poison information at the centre, told Africa Check that the “majority of the cases develop only mild symptoms”. Usually, the only treatment required for mouth exposures, Liu said, “is rinsing the mouth well and drinking water or milk.”

“It is possible for swelling after exposure to become so severe that it is difficult to breathe but it is very rare,” Liu said. “If someone is exposed to the plant and they develop severe drooling, swelling of the lower face, like the lips, tongue, cheeks, and throat, difficulty breathing, or difficulty swallowing they need to be seen immediately by medical professionals.”

‘Temporary vision loss’

Can exposure of the eyes to sap from dieffenbachia cause blindness? 

According to the Handbook of Poisonous and Injurious Plants, co-published by the New York Botanical Garden, exposure to the sap can cause extreme pain in the eyes “with the potential for severe ocular damage and vision loss”.

The US Department of Agriculture’s Forest Service notes the sap from dieffenbachia can cause “temporary vision loss and swelling of the eyelid.''

Liu told Africa Check that it was also possible for sharp oxalate crystals to scratch the surface of the eye. 

“If someone has an eye exposure to the plant and are experiencing pain they should rinse the exposed eye with room temperature water for 15 minutes. After rinsing the eye, if they continue to experience pain, swelling, changes in vision, or sensitivity to light that lasts more than 15 minutes they should be seen by a medical professional.” 

But she said she was not aware of any cases of blindness. 

‘An intense burning sensation’

Can exposure to the plant be fatal? 

Liu said it was unlikely. “I think the most appropriate thing to say is it is very unlikely to kill, but I would stress the signs and symptoms that would warrant evaluation by a medical professional, specifically swelling of the lower airway as that is the most dangerous warning sign.”

The children’s health service in the Australian state of Queensland has compiled a list of 99 plants and fungi that are considered dangerous for children and classified them according to toxicity. 

The service places dieffenbachia in both category 2 and 3, meaning it is “potentially toxic depending on the level of exposure” and an “irritant to skin or eyes from sap, prickles, spines or stinging hairs”. 

“The leaves, if chewed, will cause copious salivation and an intense burning sensation, followed by a swelling of the lips, mouth, tongue and throat. This causes difficulty in breathing and swallowing, as well as making the tongue immobile rendering the person speechless. This effect can continue for several days. Handling the plant may cause skin irritation,” the health service said.

But there is no evidence that the plant can cause blindness or is as deadly. – Vincent Ng’ethe 


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