Monday, February 9, 2009

Tony Burfield's Open Letter - Cropwatch Feb 2009

Here is Tony's open letter - please spread it across the internet and if
you can, work in any way possible to help turn back this bad science.

*The Trouble With Theories About The Oxidation of Essential Oils.*

*by Tony Burfield Feb 2009.*

* *

Judging by the response from Cropwatch supporters, many of you may have
already read about a doctoral thesis and remarks made by Lina Hagvall,
distributed via the cosmetics trade press. Many professionals have found
the reported remarks condescending, as we are well aware and may have a
wider understanding of the context of oxidized aroma materials than the
source of the remarks. But I digress. The thesis in question is entitled
"Formation of skin sensitizers from fragrance terpenes via oxidative
activation routes: Chemical analysis, structure elucidation", and Katie
Bird (Bird 2009) recently covered the story for /Cosmetics Design
Europe/, although, as with any news knocking natural products, the
article is being very widely circulated on websites dealing with health
interest and other matters. Many of us have found the Bird-penned
article makes for confusing reading: for example what is 'geraniol oil'?
A better recourse is maybe to download the thesis itself from the
University of Gothenburg website at

You will then be able to gather that the thesis is primarily concerned
with the consideration of substances without contact allergenic
properties, but which can be activated either via autoxidation in
contact with air, or via cutaneous metabolism, to reactive products
which can cause contact allergy. Primarily the study looks a five
published articles for which the author has had a major involvement,
studying the oxidation of geraniol, geranial (a conformational isomer of
citral), linalool, linalyl acetate & lavender oil. For convenience these
articles are referenced below (Hagvall /et al/. 2007; Hagvall /et/ /al/.
undated; Hagvall /et al/. 2008; Skold /et al./ 2008; Hagvall /et al/.

If I were one of Hagvall's invigilators, I would have insisted on a
re-write of a number of parts of the thesis, where the science as
presented is dubious, incomplete or, most importantly, does not present
an accurate overview of the topic. Some knowledge of industrial
practices would have aided its general acceptability as well, and a
collection of these points will constitute a future article from this

Overall this author is not saying that the elucidation of underlying
mechanisms whereby oxidized essential oils, which may be the cause of
type IV allergy and acute contact dermatitis, is not important. But an
overview to enable to put this work in perspective is importantly
missing. Further, the mention of Axel Schnuch's work (Schnuch /et al.
/2007) is selective, and a major omission to include the toxicological
reviews of Hostyneck & Maibach's on geraniol & linalool (Hostyneck &
Maibach 2007a; Hostyneck & Maibach) is almost unforgivable, however
inconvenient their conclusions to Hagvall's work.

The reader is thus left to form his/her own independent opinion on the
relevance of the study, especially against a background of an increasing
number of published studies on the anti-oxidative properties of
essential oils, the declining concentrations & use of essential oils in
fragrances generally, the use of cold-storage & nitrogen-blanketing
(amongst other measures) to prevent the oxidative deterioration of
stored essential oil and natural isolate ingredients, and the addition
of anti-oxidants, UV-filters and stabilizers to finished fragrances &
cosmetics to extend shelf-life One is also tempted to mention that a
major contributor to the cost of the studies was RIFM, a primary
instigator to the culture of toxicological imperialism which has
overtaken the regulation of cosmetics/fragrances in the West.

How does this thesis change anything? The lack of evidence of a clear
cause-effect relationship between geraniol and linalool and cases of
allergic contact dermatitis has been previously emphasized by Hostyneck
& Maibach (2004 & 2008), and Cropwatch would guess from its' own
experience that adverse end-user effects would tend to support the same
conclusion for lavender oil. Hostyneck & Maibach (2008) also comment on
the relative stability of linalool, its low oxidation rate kinetics and
speculate negatively about how readily linalool would oxidize in
fragrances & cosmetics, as well as low consumer exposure levels to the
ingredients. Great store seems to have been put on the Hagvall thesis by
IFRA/RIFM juggernaut, but considering the importance of the sensitiser
issue to the perfumery trade, and its impact on the use of natural
ingredients in perfumery, the sponsoring of just one researcher to look
(mainly) at the oxidation of geraniol & lavender oil seems an
exceptionally disproportionate response to the problem.

Unless of course you believe that RIFM sees the future of perfumery as
entirely synthetic.

Cropwatch is trying to work towards the sponsorship of toxicological
research which emphasises a risk/benefit approach towards the
elucidation of the safety of natural products - otherwise we will all
drown in a sea of over-cautious toxicological negativity, which, it is
becoming clear, has little relevance in terms of safety risks presented
to the general public from natural-product containing products.


Bird K. (2009) "Essential oils can become allergens on contact with air
and skin, says researcher." /Cosmetics-Design Europe/ 5^th Feb 2009.

Hagvall L. (2009) "Formation of skin sensitizers from fragrance terpenes
via oxidative activation routes: Chemical analysis, structure
elucidation." /PhD// Thesis University// of Gothenberg./

Hagvall L., Bäcktorp C., Svensson S., Nyman G., Börje A. & Karlberg A-T.

"Fragrance Compound Geraniol Forms Contact Allergens on Air Exposure.
Identification and Quantification of Oxidation Products and Effect on
Skin Sensitization." /Chem. Res.Toxicol//./ *20*, 807-814.

Hagvall L., Börje A. & Karlberg A-T. (date unknown) "Autoxidation of
Geranial." (Unpublished?) Manuscript.

Hagvall L., Baron J. M., Börje A., Weidolf L., Merk H. & Karlberg A-T
(2008) "Cytochrome P450 mediated activation of the fragrance compound
geraniol forms potent contact allergens." /T//oxicol. Appl. Pharmacol/.
233, 308-313.

Hagvall L., Sköld M., Bråred-Christensson J., Börje A. & Karlberg, A.T.
(2008a) "Lavender Oil Lacks Natural Protection Against Autoxidation,
Forming Strong Contact Allergens on Air Exposure." /Contact Dermatitis/
*59*, 143-150.

Hostyneck J.J. & Maibach H.I. (2004) "Is there evidence that geraniol
causes allergic contact dermatitis?" /Exogenous Dermatology/ *3*(6),

Hostyneck J.J. & Maibach H.I. (2008) "Allergic contact dermatitis to
linalool." /Perf. & Flav/. *33* (July 2008), 52-56.

Schnuch A., Uter W., Geier J, Lessmann H. & Frosch PJ. (2007)
"Sensitization to 26 fragrances to be labelled according to current
European regulation. Results of the IVDK and review of the literature."
/Contact Dermatitis/ *57*(1), 1-10.

Sköld M., Hagvall L. & Karlberg A-T (2008)."Autoxidation of linalyl
acetate, the main component of lavender oil, creates potent contact
allergens." /Contact Dermatitis/ *58*, 9-14.