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SHORT COMMUNICATION
Inhibition of Enteric Parasites by Emulsified Oil
of Oregano in vivo
Mark Force, William S. Sparks and Robert A. Ronzio*
Health Explorations Trust, Scottsdale, AZ, USA (M.F.) and Biotics Research Corporation, P.O. Box 36888, Houston, Texas 77236, USA
Oil of Mediterranean oregano Oreganum vulgare was orally administered to 14 adult patients whose
stools tested positive for enteric parasites, Blastocystis hominis, Entamoeba hartmanni and Endolimax
nana. After 6 weeks of supplementation with 600 mg emulsified oil of oregano daily, there was complete
disappearance of Entamoeba hartmanni (four cases), Endolimax nana (one case), and Blastocystis hominis
in eight cases. Also, Blastocystis hominis scores declined in three additional cases. Gastrointestinal symp-
toms improved in seven of the 11 patients who had tested positive for Blastocystis hominis. Copyright
#2000 John Wiley & Sons, Ltd.
Keywords: oregano; essential oil; Blastocystis hominis; enteric parasites; Endolimax nana;Entamoeba hartmanni.
INTRODUCTION
There is continued interest in botanical alternatives to the
drugs commonly used to treat enteric parasites. Essential
oils of culinary herbs and spices may offer a different
avenue for treating protozoal overgrowth. In this context,
the oil of Mediterranean oregano, Oreganum vulgare,is
of particular interest. This aromatic oil has been shown to
inhibit the growth of several pathogenic bacteria and
yeast (Belaiche, 1979) Kivanc and Akgul, 1986). Orally
administered oil of oregano ingestion was found to
eradicate common fowl parasites in infected chickens and
pheasants (Ninkov, 1996). Therefore, the present study
was designed to examine the effects of oil of oregano in
symptomatic patients with enteric parasites.
MATERIALS AND METHODS
Thirty-three adult patients with chronic gastrointestinal
complaints and fatigue submitted two purged faecal
specimens, which were analysed by a clinical laboratory
(Diagnostic and Educational Laboratory—Institute of
Parasitic Diseases, Phoenix, Arizona). Parasites per high
power field (400X) were counted. The scores were based
on the means of four to six fields (nil for no parasites
detected; 1 for 1–5 parasites; 2 for 6–10; 3 for 11–
15; and 4 for >15). In addition, the patients completed
a symptom and risk assessment questionnaire. After
obtaining informed consent for the protocol, approved by
a Review Board, patients with enteric parasites were
supplemented with a preparation of emulsified oil of
oregano (A.D.P. from Biotics Research Corporation,
Rosenberg, Texas 77471). Fourteen patients (four men,
10 women, ages 24–56) with parasites were administered
four tablets providing 200 mg of emulsified oil t.i.d. with
meals. No other dietary changes or therapeutic interven-
tions were employed. After 6 weeks of supplementation,
patients submitted a second set of purged stool specimens
for parasite analysis, and they completed a follow-up
questionnaire. Statistical analysis of parasite scores
employed the sign test.
RESULTS
Thirty-three patients with gastrointestinal complaints
who reported one or more of the following factors which
could increase the risk of parasitic infections: recent
foreign travel, exposure to small children in daycare, out-
of-doors lifestyles and camping, lowered immunity,
ownership of household pets, use of untreated well
water, and consumption of uncooked salad greens, were
selected for this study. Parasites were detected in stool
specimens from 14 of these patients. As summarized by
Table 1, eight patients initially tested positive for Blasto-
cystis hominis; Entamoeba hartmanni was detected in
another four patients; and one patient had Endomalix
nana.
Thirteen of the 14 patients with parasites completed
the supplementation protocol and submitted follow-up
stool specimens. Parasites could no longer be detected in
10 patients (77%), including those who initially tested
positive for Entamoeba hartmanni, Endolimax nana and
Blastocystis hominis with scores <2(Table 1). In
addition, parasite scores decreased for another three
subjects (23%) with Blastocystic hominis, though the
parasite was still detectable by the end of the study. The
likelihood of obtaining decreased parasite scores for 13
of 14 individuals by chance was highly improbable
(p<0.0006). Commensurate with the reduction in
parasite scores after supplementation with oil of oregano,
PHYTOTHERAPY RESEARCH
Phytother. Res. 14, 213–214 (2000)
Copyright #2000 John Wiley & Sons, Ltd.
* Correspondence to: Dr R. A. Ronzio, Biotics Research Corporation, P.O.
Box 36888, Houston, Texas 77236, USA.
Contract/grant sponsor: Biotics Research Corporation.
Received 25 May 1999
Revised 28 July 1999
Accepted 7 September 1999
seven of the patients who initially tested positive for
Blastocystic hominis reported amelioration of symptoms,
including bloating, GI cramping, alternating diarrhoea
and constipation and fatigue.
DISCUSSION
To the best of our knowledge, this is the first report of
antiparasitic effects of oil of oregano in humans. Whether
the improvement of symptoms in response to oregano oil
was due to the inhibition of undetected microorganisms
or to the elimination of parasites cannot be differentiated
by this study. A variety of studies and case reports have
reported Blastocystic hominis in faecal specimens of
patients with gastrointestinal symptoms (Carbajal et al.,
1997; Shlim et al., 1995). However, this observation may
reflect an association, rather than a causative agent. It
should be noted that the prevalence of this parasite can be
high, ranging from 9.5% to 18% among clinic stool
specimens (Zuckerman et al., 1990).
In considering the oral use of oil of oregano, an
effective delivery is an important consideration. Expo-
sure of gastrointestinal mucosa to concentrated (non-
emulsified) essential oils can cause localized irritation,
especially with prolonged usage. Emulsification of oil of
oregano yielded stable particles with an average diameter
of 0.5 mm.
This process increases the surface area by about six
orders of magnitude, thus the total surface area of an
emulsion generated from 200 mg (four drops of oil)
would theoretically equal the total luminal surface of the
small intestine (an estimated 200 m
2
). The clinical
significance of Blastocystis hominis remains controver-
sial. Case reports of the amelioration of gastrointestinal
symptoms and systemic complaints upon eradication of
Blastocystis hominis, Endolimax nana and Entamoeba
hartmanni suggested these organisms may act as weak
pathogens in susceptible individuals (Burnstein and
Liakos, 1983; Schirmer et al., 1998). The effect of
emulsified oil of oregano on well-established enteric
pathogens, such as Entamoeba histolytica and Giardia
lamblia, warrants further study.
Acknowledgement
This research was supported by Biotics Research Corporation.
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Table I. Summary of faecal parasite scores, pre- and post-
treatment with emulsified oil of oregano
Number of Parasite score
Parasite detected patients Before Post-treatment
Blastocystis hominis 5 1 nil
2 2 1
1 4 2
Entamoeba hartmanni 4 1 nil
Endomalix nana 1 2 nil
Total 13 10 3 p<0.0006
214 M. FORCE ET AL.
Copyright #2000 John Wiley & Sons, Ltd. Phytother. Res. 14, 213–214 (2000)