HERB - methyl salicylate problem research (long)

[Gaylin Walli]

Herth (and others privately) asked:

>I certainly appreciate you warnings and cautionary notes!  I'd be glad to
>see what you have to say about some of the so-called scientific studies.

I'll warn you now that this is really long and represents research I'm
still looking into. But in the spirit of education and sharing, I'll put
down what I've gotten so far. Look into these things and decide for
yourself. I'm untrained, unlicensed, and merely a curious party when
it comes to researching some of this stuff. Ask someone who knows
and do research for yourself. This is the only way to learn.

When I was looking up the reasons why not to include wintergreen
oil in my sore muscle rub (like tiger balm) a lot of people would blindly
tell me "Don't use that oil. People die from it." Caution seemed to be the
order of the day in that regard, so I started looking up the references I
could find on the subject of wintergreen oil.

I'll ignore for a moment, the stuff I've found on the web, because the
vast majority of it comes from sites of people without knowledge of
essential oil safety. They are merely repeating what they've read.
The best book I got on the topic of essential oil safety was by Tisserand
and Balacs and called "Essential Oil Safety: A Guide for Health Care
Professionals" (ISBN 0443052603, May 95). I also looked into the
AMA Guide to Poisonous Plants and a book called "Plant Aromatics"
by Martin Watts.

Tisserand is better as detailing the studies, scientific or otherwise,
that were done on wintergreen consumption. However, the danger
in that detail is the assumption made by the authors on the results
of the studies. As I understood the writeup on wintergreen and birch
oils, both of which contain mathyl salicylate, I was struck by several
problems with the studies and anecdotal evidence they reported on.

I'll quote a few passages so you can understand why I have problems.
And if you disagree or if you can point me to better studies or  if you
can point out flaws in my questioning, I'd very much appreciate hearing
your take....keep in mind that I'm taking these quotes out of context. You
may get a different interpretation if you're reading along with the book
in hand.

Tisserand and Balacs write:

>"Methyl salicylate can be absorbed transdermally in sufficient quantities
>to cause poisoning in humans."

This means that the main ingredient in wintergreen and birch oil can
be absorbed through the skin in quantities large enough to poison a
human.
      The study they quoted had three problems with it as far as
I see. First, it was conducted on rabbit skins. Tisserand and Balacs
directly state that this is a problem when they say "The acute dermal
LD figures should be regarded with perhaps even more circumspection,
as we have very little idea how well animal data would extrapolate
to the human siutation. They probably give no more useful indication
of the toxicity of dermally applied essential oils in relation to
aromatherapy" (pg. 47). What they mean is studies conducted on rabbits
can be compared to how humans might be affected because rabbit
skin doesn't behave the same as human skin. The authors confirm this
when they say that absolutely "no evidence exists [that human skin
and rabbit skin absorb the same oils at the same rates] and it is
*believed* that, in general, the absorption of chemicals is significantly
higher through animal skin" (pg. 47, emphasis mine).
      As I read it, the study quoted by the authors is a well-written one,
but I have at least one more concern. My second concern is that the systemic
toxicity (the poisonous nature to the entire living system of a body) of
methyl salicylate was tested on DAMAGED skin, not healthy skin of these
animals. The studies to which they refer regarding dermal toxicity, even
over time, were all extrapolated from data taken from animals who were
treated with very high doses, every single day over three months (I've
lost the page number for this one, sadly, but its written in their book).

Now, in another portion they write:

>"In the years 1926,1928, and 1939-1943 427 deaths occured in the USA from
>methyl sal poiosoning." (Tisserand quoting Davison C et al 1961 on the
>metabolism and toxicity of methil salisylate. Journal of pharmacology and
>Experimental Therapeutics 132:207-211)

What this quote means is that for specific years, quite some time ago,
people died from methyl salycylate poisoning. But how did they die?
Did they drink it directly? You can buy it that way. Did they drink it
in its natural form as part of the plant? They don't say. Did they rub
it on their skin? Did they have an allergic reaction that was caused
by the substance? Again, they don't say. The most damning fact, in my
mind, is that this quote makes no mention of the high number of deaths
that are the direct result of suicidal overdose from those substances
which contain high quantities of methyl salicylate.
      Instead of relying on Tisserand as a secondary source in this
matter, I think I would like to see where Davison gathered this
data and how much of it was the direct result of intentional
overdose. To extrapolate potential for toxicity from this data,
even internally taken, would seem foolish without further
examination of the death stats that Davison viewed. I'm trying to
get the Davison study through interlibrary loan (so far, without
success, so I may have to try a research library next).

Tisserand also quotes another study. And this one was of realy interest
to me, because of the topical application implications (as opposed to the
implications of consuming it orally):

>"Topically applied methyl salicylate can potentiate the antigoagulant
>effect of warfarin causing side-effects such as internal hemorrhage.  A
>similar interaction is possible ...with other anticoagulants such as
>aspirin and heparin."  (Again, Tisserand, quoting Le Bourhis B, Soenen A-M
>1973 Recherches sur l'action psychotrope de quelques substances aromatiques
>utilisees en alimentation. Food and cosmetix Toxicology 11:1-9)

I can't read French. I'll admit that right out. I have no way to study this
statement's source directly short of having someone read it to me in
English. My next course of action is to look into exactly how long stuff
sticks around in the skin, in the blood, and in the liver. However, until
that research is done I have not stopped using the substance in my balms.
I do, however, put a strong warning on the labels. And I make sure that
the total oil in the batch is very small. I worked it out one time and the
total oil is perhaps .06 percent of all the ingredients.
      Another thing I looked into was the production of wintergreen and birch
oil for distribution in the United States. And I found that roughly 99% of the
oil distributed for each of these sources was SYNTHETIC and said to posses
no threat to human life (other than possibly making you dreadfully sick if
you drank a cup of the stuff).

>Martin Watts in Plant Aromatics, set 4 states "MANY OTHER REPORTS OF
>ADVERSE EFFECTES ARE RECORDED (emphasis his, not mine), a comprehensive
>survey is to be found in  DeSmet P. 1992 Adverse Effects of Herbal Drugs.
>Springer-Verlag. Heidelberg "

My initial response to this was "yeah? so what? people have adverse effects
from drinking the wrong water when they go on vacation." It's worth looking
into, though, but no library I've tried has been able to get the 
original source
for this. But the big question here is WHAT OTHERADVERSE EFFECTS? In good
writing, all the effects would be listed. A good study would NOT say "X, Y, Z
effects, and others." All the effects would be listed.

>Watt again "Methyl salicylate is freely absorbed by the skin and can lead
>to high blood levels of salicylic acid. Davison C. et al 1961 J. Pharmacol.
>Exp. Ther. 132,207=11"

For how long does it stay in the body? How long do the blood levels last?
The skin is a wonderful organ for getting rid of all kinds o nasties. The
liver is too. So how does Davison account for this? I don't know.

There you have it. This is what I've come up with so far.  Sorry about the
length and sorry there's nothing definite in here. I wish there was. If you've
got pointers to more studies, I'd love to see them. Even if they're not at
all about the methyl salicylate. I'd be interested in any studies people have
on the transdermal effects of essential oils.

Jasmine
Iasmin de Cordoba
gwalli at infoengine.com

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