In an answer to another question, the following story was cited.

Another interesting one that demonstrates both the placebo and nocebo effect in one study is a study done by Japanese researches on 57 high school aged boys. They selected these boys based on the fact that when exposed to Lacquer trees, these boys would get a severe rash, much like is common with poison ivy. They then blindfolded the boys and proceeded to brush one of their arms with the Lacquer tree leaves and the other with an innocuous leaf that would have no effect. They told them however that the arm brushed with the laquer tree was brushed by the harmless leaf and the one brushed by the harmless leaf they were told was brushed by the Lacquer tree leaf. What followed was a rash developed on most of the boys arms that were brushed by the harmless leaf and the other arm that was actually brushed by the Lacquer leaf that should have caused a rash was completely fine in nearly every case.

I found this extraordinary, and decided to follow it up.

The original answer cites Today I Found Out.

That cites The Skeptic's Dictionary for the story.

That cites a defunct journal article, called Hippocrates, which, using the WayBack machine, can be found here.

It references... umm... "a review" of "scattered studies" in Medline by Dr Robert Hahn who is still at the CDC.

A quick skim of the 134 articles about nocebo at Medline (via PubMed) suggested nothing relevant prior to November 1999.

I haven't contacted Dr Robert Hahn; I am not sure he would like his duties at the CDC interrupted with a question from a random about a quick literature survey he did two decades ago.

Does anyone have any idea where this study was originally from or if anything like it has been repeated?

  • Hmm, I don't read the Hippocrates article in such a way that it references Hahn for that particular experiment; it could just be one of the "30 references" from Medline. Commented Aug 27, 2011 at 19:27

2 Answers 2


Yes, a nocebo study did find that rashes could appear on the wrong arm due to suggestion.

As this was a question whose "trail runs dry", I figured I'd give context to how I found it, first, but I have found the study in question, and before I continue, here's the interesting line in the summary at the end:

The effect of suggestion upon the development of contagious dermatitis was proven to be statistically significant at the 0.1% level.

So as I said, before I reference the paper, here's how I found it. First, I went to Google Scholar and did a search using the most important words in the context - Lacquer Tree Nocebo. The first result I found (this was scholar.google.com.au, so it might vary by region) was called "Placebo, meaning, and health", but wasn't available freely... fortunately, the same article was available a few links further down, and the paper in question is here. A quick search found "Lacquer" in a sentence with "46" as a reference number, and in the Reference List, we find

  1. Ikemi Y. A psychosomatic study of contagious dermatitis. Kyoshu Journal of Medical Science 1962;15:335-50.

Which, given the date of 1962, was clearly going to be the original paper... and indeed, Google Scholar found the article itself, available here here. (UPDATE: the original link no longer works, but I've found an alternative, for those who want to see it - you can always do a google search for the title of the article, if the new link fails)

The full summary at the end says this:

An experimental study on the effect of suggestion on the outbreak of contagious der­matitis induced by wax trees and lacquer trees has been performed with fifty-seven male subjects, aged fifteen to eighteen years.

I: In the leaf-contact experiment, in 13 subjects with "strong reaction" reported on the questionnaire, the definite effect of suggestion was seen in 84.6% of the subjects.

II: In the experimental application of the extract of the poisonous trees in 15 subjects with a "moderate reaction" reported on the questionnaire, the effect of suggestion was seen in 56.2% of the subjects.

III: In the leaf-contact experiment, in the dark room in 5 subjects with "no previous experience" reported on the questionnaire, the effect of suggestion was seen in 40.0% of the subjects.

IV: In the leaf-contact experiment in the dark room and experimental application of the extract with 16 subjects with "no previous reaction" reported on the questionnaire the effect of suggestion was seen in 23.5% of the subjects.

V: In the summary of the results of the above experiments, the reactivity was actually seen in as high as 89.5% of the subjects. In 35.3% constitutional factors seem to play the dominant role with the exception of 2 cases where the effect of suggestion also was distinctly seen. In 51.0%, suggestion clearly predominates over the constitutional factors. The percentage of subjects who showed no reaction to either suggestion or poison was 13.7% (Table 13).

VI: The effect of suggestion upon the development of contagious dermatitis was proven to be statistically significant at the 0.1% level.

VII : The percentage of allergic family history was higher in the group of allergic reac­tion than in the auto-suggestive group.

VIII: Skin pathology of acute eczema was produced by the conditioning procedure and the histological findings of thus induced skin reaction were proven to be similar to the skin pathology produced by actual contact with the lacquer extract.

Note: I had to manually correct my pdf reader's interpretation of the content (which, among other things, kept interpreting percent symbols as "96", and it saw "III" as "IH"). As such, I may have missed a couple of corrections.

And although it doesn't prove anything, I feel it is worth noting that it is referenced in a number of books on the subject, so I'm assuming that if flaws were found in the experiment, they would be well-known. But I could be mistaken.

The other interesting thing, which isn't in the summary section, is that the control leaf was a Chestnut leaf, and there were two distinct "poisonous" leaves - from the Japanese Wax Tree, and from the Chinese Lacquer Tree.

  • 8
    From the summary you quoted, it looks like the presence and severity of the rashes was determined by self-reporting and not by any medical examination. In my mind, this makes the conclusion more ambiguous. Placebos can have a strong effect on the perception of symptoms with little to no measurable physical improvement. It seems likely that the same is true of a nocebo.
    – KSmarts
    Commented Apr 8, 2015 at 21:42
  • Very interesting. It's a complicated series of experiments, with controls groups of varying values. It would be nice to see some replications. I wonder to what degree the rashes are a function of scratching (which seems, to my naive mind, far more influenceable by suggestion, and far more location-specific than any other mechanism that I can think of for the brain to cause one bit of skin to react and not another.)
    – Oddthinking
    Commented Apr 9, 2015 at 1:48
  • @KSmarts - that would strongly explain the presence of rashes on the chestnut arm, but it wouldn't explain why the lacquer/wax arm was asymptomatic despite the actual leaf being "poisonous" (I use quotes because it's general toxicity, not poisonousness, that is relevant here, since the leaf isn't being ingested).
    – Glen O
    Commented Apr 9, 2015 at 3:43
  • I just moved some weeds that I pulled up yesterday, and have a mild rash where they touched the back of my hand. Now I am convinced it is all psychosomatic because I've been reading this thread.
    – Oddthinking
    Commented Apr 9, 2015 at 5:40
  • Did the study actually say anything about rashes NOT developing with the poison, or only about rashes developing without the poison? The latter is still highly interesting but I think the main point here in the question is the first one(?)
    – kutschkem
    Commented Oct 18, 2022 at 7:35

The review from Dr. Hahn you're looking for is most likely the following article:

Hahn RA. The nocebo phenomenon: concept, evidence, and implications for public health. Prev Med. 1997 Sep-Oct;26(5 Pt 1):607-11.

Link to Pubmed and link to the article on ScienceDirect.

Unfortunately, the study about the rash is not mentioned in that review. It only mentiones other studies, e.g. "A double-blind study of symptom provocation to determine food sensitivity." (free full text).

  • Wow! So the trail runs dry.
    – Oddthinking
    Commented Mar 1, 2011 at 6:24

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