JEWELWEED, POISON IVY, AND HOMER SIMPSON

“Poison Ivy!”

It’s a name that strikes fear. Everyone seems to have, or know someone who has, a story of horrific dermatitis caused by this legendary member of the Sumac family. Most people have heard the axiom, “Leaves of three, let it be,” but that’s a poor guide for identification. Many common, harmless plants, including Wild Strawberry, have a three-leaved appearance. Fewer people have heard the second part of the “leaves of three” adage: “If there’s hair, leave it there,” a reference to the Poison Ivy vine’s tendency to appear hairy as it gets older (the “hairs” are adventitious roots, which provide a means for a plant to spread by climbing). It’s a helpful field mark, but not present when Poison Ivy is growing on the ground. (Fewer still have heard Homer Simpson’s third line of the Poison Ivy poem, “Leaves of four, eat some more!”)

 

But this article isn’t about identifying Poison Ivy (Toxicodendron radicans). For that, see the link I posted below. This is about a potential treatment for the rash caused by exposure to T. radicans.

 

When I was first introduced to the plant, I was also shown how to mash the leaves of another native plant: Impatiens capensis, also known as Jewelweed or Spotted Touch-me-not. Applying mashed leaves, I was taught, would cure the irritation and itching of a case of Poison Ivy. Added in for good measure was a supposedly Native American claim that wherever you found Poison Ivy, you would also find Jewelweed growing close by.

 

These claims were so pleasing to my young naturalist’s ears, that I shared them readily and saw them repeated by numerous sources, both on- and offline. But I never had the chance to test them for myself. Up to this point, I’ve somehow avoided ever getting Poison Ivy, except for the time when I wanted to see if I was immune to it and spent 7 days rubbing larger and larger pieces of cut stem on my hand (I eventually got a small rash). I have applied the mashed Jewelweed leaves to a nasty case of Stinging Nettles (another reported use), but they gave me no relief.

 

Most of the articles that cite research into Jewelweed’s effectiveness reference a study from 1958 in which a Jewelweed treatment was compared with other Poison Ivy dermatitis treatments. In the Jewelweed group, 108 out of 115 patients were entirely relieved of their symptoms within 2 or 3 days. Sounds good, right? What nearly every reference to this study fails to mention, however, is a follow up study from 1980, in which two researchers questioned whether it was not the Jewelweed, but the water in which it was mixed, that affected the Poison Ivy. They tested their hypothesis by treating some Poison Ivy rashes with water, some with Jewelweed, and some with nothing. Their results pointed to Jewelweed having no effect on the rash and that plain water may have a slight benefit. Another study in 1997, seemed to confirm these findings. Things were not looking good for Jewelweed.

 

As with all studies, however, it’s good to dig into the methods to get a complete picture. The 1958 study made use of the entire plant, while the latter two used stem extracts. Could the stem extracts lack the compounds that affect Poison Ivy?

 

A study in 2012 decided to answer this question. Different groups of volunteers with Poison Ivy were treated with Jewelweed extracts, fresh plant mashes, soaps made with Jewelweed extracts, and water and dish soap. The researchers reported, “we can say with a 95% confidence interval that jewelweed mash is effective in decreasing the development of [Poison Ivy rash].” But they go on to say that even more effective than Jewelweed is soap and water, and that the Jewelweed soaps (containing Jewelweed extracts) were no more effective than dish soap. The researchers hypothesized that Jewelweed may show effectiveness because it contains saponins, chemical compounds (glycosides) that produce soap-like foam when mixed with water.

 

These researchers did a follow up study in 2015 to test their hypothesis, and the results confirmed it. A Jewelweed plant mash showed some reduction in Poison Ivy rash, but extracts of the Jewelweed saponins showed a greater reduction, as did the groups treated with soap and water. The greatest reductions were found in two groups: those treated with a double strength saponin extract and those treated with soap/water.

 

So, where does that leave us? Research shows that Jewelweed is indeed an effective cure for Poison Ivy, but soap and water are more effective. Here’s why: the component of Poison Ivy that causes a rash is an oil called urushiol. The oil needs to come in contact with your skin in order for a reaction to develop. The longer the exposure, the worse the rash. Since urushiol is an oil, water alone does a poor job of removing it, but soap works well. When you’re in your backyard or out on the trail and you think you have come into contact with Poison Ivy sap (and the urushiol oil within it), wash the affected area as soon as possible with soap and water in order to remove the oil. Soap and water works best, but if you don’t have any around and you spot some Jewelweed, mash it up and rub it in! Jewelweed (and the soap-like saponins within it) are the next best treatment.

~Bill

Further reading:

1.      Identifying Poison Ivy:  http://msue.anr.msu.edu/news/identifying_poison_ivy_isnt_always_easy_to_do

2.      About saponins: https://en.wikipedia.org/wiki/Saponin

3.      Medical attributes of Jewelweed: http://klemow.wilkes.edu/Impatiens.html

 

Sources:

1.      Guin, Jere D., and Ruth Reynolds. "Jewelweed treatment of poison ivy dermatitis." Contact dermatitis 6.4 (1980): 287-288.

2.      Lipton, R. A. "The use of impatiens biflora (jewelweed) in the treatment of rhus dermatitis." Annals of allergy 16.5 (1958): 526.

3.      Long, David, Noel H. Ballentine, and James G. Marks Jr. "Treatment of poison ivy/oak allergic contact dermatitis with an extract of jewelweed."Dermatitis 8.3 (1997): 150-153.

4.      Motz, Vicki A., et al. "Efficacy of the saponin component of Impatiens capensis Meerb. in preventing urushiol-induced contact dermatitis."Journal of ethnopharmacology 162 (2015): 163-167.

5.      Motz, Vicki Abrams, et al. "The effectiveness of jewelweed, Impatiens capensis, the related cultivar I. balsamina and the component, lawsone in preventing post poison ivy exposure contact dermatitis." Journal of ethnopharmacology 143.1 (2012): 314-318.