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As a kid, I was taught during my summer camp that jewelweed, a plant commonly found throughout North America, is an effective treatment for poison ivy and stinging nettle.

Indeed, I've used it myself after touching stinging nettle, and felt immediate relief. However, I now wonder if I simply experienced a placebo effect.

There are other claims of its effectiveness as a cure-all, however I am hesitant to take an unreferenced claim of the results of a 1958 study at face value:

It apparently contains chemicals that neutralize the components responsible for the skin-irritating effects of poison oak, poison ivy and other irritants including stinging nettle, insect bites and ringworm. Folk remedies also recommend jewelweed poultices as treatment for minor injuries such as bruises, cuts, burns, sores, sprains and warts.

According to Varro Tyler in his book Herbs of Choice, a 1958 study compared jewelweed to "standard poison ivy dermatitis treatments," including corticosteroids. The researchers found that the plant was effective in treating 108 out of 115 patients, leading to complete symptom relief within two to three days.

Is there any scientific support to the claim of this plant providing relief from skin irritants, particularly those caused by poison ivy or stinging nettle (although research showing benefits against other irritants would be acceptable substitute data)? Is the 1958 study referenced above legitimate?

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Summary:

The stems of impatiens capensis has been shown to have no measurable benefit over plain water in treating poison ivy or poison oak rash. However, the seed fruit do contain compounds with significant anti-itching activity, and likely help relieve the itch of poison ivy, if not the rash.

Sources

I found several references to the 1958 study, apparently conducted by R.A. Lipton. However, I could not find a copy of the study itself (no doubt due at least in part to its age).

The consensus appears to be that Lipton's study involved treating 115 patients with an existing poison ivy rash with "jewelweed preparations", and that 108 of the 115 patients "responded most dramatically to the topical application of [jewelweed]".

Countering this claim is a 1997 study by Long, Ballentine, and Marks that found no discernable difference in the treatment of urushiol (the allergic resin of poison ivy/oak) rash between crushed jewelweed stem and distilled water.

However, a biology student at Wilkes University by the name of Sarah Becker did an analysis of the existing research in 2001, and found that a possible explanation for the disparity is that the part of the plant used may be relevant to the effectiveness:

Perhaps the reason for the varying investigative results lies in what part of the plant is used. Researchers in Japan showed that the pericarp of Impatiens balsamina contained three dinaphthofuran-7,12-dione derivatives (Ishiguro et .al. 1998). These three compounds all had significant anti-itching activity. However two of the three studies described above used stem extracts (Guin & Reynolds 1980, Long et. al. 1997), while only one used the entire plant (Lipton 1958). Also these compounds only serve to reduce itching, not the rash. This may, however, be significant since poison ivy rash can be spread by itching.

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