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Final report on the safety assessment of Mentha Piperita (Peppermint) Oil, Mentha Piperita (Peppermint) Leaf Extract, Mentha Piperita (Peppermint) Leaf, and Mentha Piperita (Peppermint) Leaf Water.

Mentha Piperita (Peppermint) Oil, Mentha Piperita (Peppermint) Leaf Extract, Mentha Piperita (Peppermint) Leaf, Mentha Piperita (Peppermint) Leaf Water are obtained from the Mentha piperita plant. The oil is currently used in cosmetic formulations as a fragrance component, but previously had been also described as a denaturant. The extract and leaves are described as biological additives, but only the extract is reported to be used. Peppermint Water is described as a flavoring agent or fragrance component, but is not currently in use. Peppermint Oil is used at a concentration of < or = 3% in rinse-off formulations and < or = 0.2% in leave-on formulations. Peppermint Oil is composed primarily of menthol and menthone. Other possible constituents include pulegone, menthofuran, and limone. Most of the safety test data concern Peppermint Oil. The oil is considered to present the "worst case scenario" because of its many constituents, so data on the oil were considered relevant to the entire group of ingredients. Peppermint Oil was minimally toxic in acute oral studies. Short-term and sub-chronic oral studies reported cystlike lesions in the cerebellum in rats that were given doses of Peppermint Oil containing pulegone, pulegone alone, or large amounts (>200 mg/kg/day) of menthone. Pulegone is also a recognized hepatotoxin. Repeated intradermal dosing with Peppermint Oil produced moderate and severe reactions in rabbits, although Peppermint Oil did not appear to be phototoxic. Peppermint Oil was negative in the Ames test and a mouse lymphoma mutagenesis assay but gave equivocal results in a Chinese hamster fibroblast cell chromosome aberration assay. In a carcinogenicity study of toothpaste and its components, no apparent differences were noted between mice treated with Peppermint Oil and those treated with the toothpaste base. Isolated clinical cases of irritation and/or sensitization to Peppermint Oil and/or its constituents have been reported, but Peppermint Oil (8%) was not a sensitizer when tested using a maximization protocol. It was expected that dermal absorption of Peppermint Oil would be rapid, following that of menthol, a major component, but in no case would be greater than absorption through the gastrointestinal tract. Because of the toxicity of pulegone, the safe concentration of this constituent was limited to < or = 1%. This concentration was achievable both by controlling the time of harvest and processing technique. There is evidence that menthol can enhance penetration of other agents. Formulators were cautioned that this enhanced penetration can affect the use of other ingredients whose safety assessment was based on their lack of absorption. With the limitation that the concentration of pulegone in these ingredients should not exceed 1%, it was concluded that Mentha Piperita (Peppermint) Oil, Mentha Piperita (Peppermint) Extract, Mentha Piperita (Peppermint) Leaves, Mentha Piperita (Peppermint) Water are safe as used in cosmetic formulations.

Animals↗

Spasmolytic effect of peppermint oil in barium during double-contrast barium enema compared with Buscopan.

AIM: To evaluate the efficacy of peppermint oil in barium as a spasmolytic agent during a double-contrast barium enema (DCBE). MATERIALS AND METHODS: A total of 383 DCBEs with positive results from occult blood tests were assessed. Patients were assigned to one of four groups: peppermint in barium (n=91), peppermint in tube (n=90), Buscopan (n=105), or no treatment (n=97). After a screening sigmoidoscopy, the DCBEs were performed using air as a distending gas. In the Buscopan group, the DCBE was performed with an intramuscular injection of 20mg Buscopan at the start of the examination. Patients in the no-treatment group underwent DCBE without any spasmolytic agent. A peppermint oil preparation (30ml) was mixed in the barium solution for patients in the peppermint-in-barium group, and the same dose of peppermint oil was included in the enema tube in the peppermint-in-tube group. The presence of spasm on a series of spot films was evaluated without information about the type of spasmolytic agent used. RESULTS: The percentage of patients in the four groups (no treatment, Buscopan, peppermint in tube, and peppermint in barium) with absence of spasm in the entire colon on the series of spot films was 13.4, 38.1, 41.8, and 37.8%, respectively. In the group using peppermint oil or Buscopan, the rate of patients with non-spasm examination was higher than that in no-treatment group (p<0.0005). Peppermint oil had the same spasmolytic effect as the systemic administration of Buscopan in the transverse and descending colon. Peppermint oil had a stronger effect in the caecum and the ascending colon than a Buscopan injection (p<0.005). There was no advantage to placing peppermint oil in the enema tube over mixing it in the barium solution. A total of 157 polyps were found during the DCBE procedures, and no differences were observed in the number of lesions among the four groups. Peppermint oil did not impair image quality. CONCLUSION: Barium solution mixed with peppermint oil was safe and effective for the elimination of colonic spasm during the DCBE procedure, and it could be used instead of Buscopan.

Barium Sulfate↗

A review of the bioactivity and potential health benefits of peppermint tea (Mentha piperita L.).

Peppermint (Mentha piperita L.) is one of the most widely consumed single ingredient herbal teas, or tisanes. Peppermint tea, brewed from the plant leaves, and the essential oil of peppermint are used in traditional medicines. Evidence-based research regarding the bioactivity of this herb is reviewed. The phenolic constituents of the leaves include rosmarinic acid and several flavonoids, primarily eriocitrin, luteolin and hesperidin. The main volatile components of the essential oil are menthol and menthone. In vitro, peppermint has significant antimicrobial and antiviral activities, strong antioxidant and antitumor actions, and some antiallergenic potential. Animal model studies demonstrate a relaxation effect on gastrointestinal (GI) tissue, analgesic and anesthetic effects in the central and peripheral nervous system, immunomodulating actions and chemopreventive potential. Human studies on the GI, respiratory tract and analgesic effects of peppermint oil and its constituents have been reported. Several clinical trials examining the effects of peppermint oil on irritable bowel syndrome (IBS) symptoms have been conducted. However, human studies of peppermint leaf are limited and clinical trials of peppermint tea are absent. Adverse reactions to peppermint tea have not been reported, although caution has been urged for peppermint oil therapy in patients with GI reflux, hiatal hernia or kidney stones.

Animals↗

Investigation of the effects of peppermint oil and valerian on rat liver and cultured human liver cells.

1. The aim of the present study was to investigate the effects of peppermint oil and valerian on rat liver and cultured human hepatoma cells. 2. Rats received a single oral dose of peppermint oil (8.3-830 microL/kg) or valerian (0.31-18.6 g/kg), or daily oral doses of 83 microL/kg peppermint oil or 3.1 g/kg valerian for 28 days. After 24 h, rats were anaesthetized and measurements made of bile flow, liver function and in vivo sinusoidal area. Livers were then removed for histology. 3. Bile flow was unaffected by any treatment, except acute high-dose peppermint oil (830 microL/kg; 70% increase in flow). No change in liver enzyme activity was found, except for a 45% increase in alkaline phosphatase after chronic peppermint oil. No change in sinusoidal area in vivo or in histology was found following any treatment, although pretreatment with carbon tetrachloride reduced sinusoidal bed area and produced histological damage. Incubation of human hepatoma cells with 0.5 microL/mL (but not 0.05 microL/mL) peppermint oil or 20 mg/mL (but not 2 mg/mL) valerian resulted in increased cell death. 4. In conclusion, the present study demonstrated in vitro toxicity of high doses of valerian and peppermint oil in cultured human hepatoma cells and, at doses 2-3 orders of magnitude greater than those recommended for human use, an increase in rat bile flow after acute peppermint oil and an increase in alkaline phosphatase after chronic peppermint oil.

Animals↗

Virucidal effect of peppermint oil on the enveloped viruses herpes simplex virus type 1 and type 2 in vitro.

The virucidal effect of peppermint oil, the essential oil of Mentha piperita, against herpes simplex virus was examined. The inhibitory activity against herpes simplex virus type 1 (HSV-1) and herpes simplex virus type 2 (HSV-2) was tested in vitro on RC-37 cells using a plaque reduction assay. The 50% inhibitory concentration (IC50) of peppermint oil for herpes simplex virus plaque formation was determined at 0.002% and 0.0008% for HSV-1 and HSV-2, respectively. Peppermint oil exhibited high levels of virucidal activity against HSV-1 and HSV-2 in viral suspension tests. At noncytotoxic concentrations of the oil, plaque formation was significantly reduced by 82% and 92% for HSV-1 and HSV-2, respectively. Higher concentrations of peppermint oil reduced viral titers of both herpesviruses by more than 90%. A clearly time-dependent activity could be demonstrated, after 3 h of incubation of herpes simplex virus with peppermint oil an antiviral activity of about 99% could be demonstrated. In order to determine the mode of antiviral action of the essential oil, peppermint oil was added at different times to the cells or viruses during infection. Both herpesviruses were significantly inhibited when herpes simplex virus was pretreated with the essential oil prior to adsorption. These results indicate that peppermint oil affected the virus before adsorption, but not after penetration into the host cell. Thus this essential oil is capable to exert a direct virucidal effect on HSV. Peppermint oil is also active against an acyclovir resistant strain of HSV-1 (HSV-1-ACV(res)), plaque formation was significantly reduced by 99%. Considering the lipophilic nature of the oil which enables it to penetrate the skin, peppermint oil might be suitable for topical therapeutic use as virucidal agent in recurrent herpes infection.

Acyclovir↗

Efficacy of peppermint oil as an antispasmodic during endoscopic retrograde cholangiopancreatography.

BACKGROUND: During endoscopic retrograde cholangiopancreatography (ERCP), hyoscine-N-butylbromide (Buscopan) or glucagon is used to inhibit duodenal motility. However, they may cause adverse effects. Peppermint oil has an antispasmodic effect and is used as a less hazardous antispasmodic during colonoscopy and upper gastrointestinal endoscopy. The purpose of the present paper was therefore to investigate peppermint as an antispasmodic for ERCP. METHODS: Forty patients were enrolled prospectively. They were assigned to four groups according to the peppermint oil concentration and site of administration: group 1, 20 mL of 1.6% solution around duodenal papilla; group 2, 20 mL of 1.6% solution both to the antrum of the stomach and around the duodenal papilla; group 3, 20 mL of 3.2% solution around the duodenal papilla; and group 4, 3.2% solution both to the antrum and around the duodenal papilla. Glucagon or hyoscine-N-butylbromide was added when duodenal peristalsis was not adequately diminished. Sixteen patients undergoing ERCP with glucagon were employed as historical controls. RESULTS: The ERCP was attempted in all except one patient in group 2 who had bleeding from invaded tumor to the duodenum. Peppermint administration equally reduced duodenal motility in the groups. Duodenal movement was none or mild in 69.2% of patients. The ERCP was successfully performed with peppermint alone in 91.4% of patients (37/39). Glucagon or hyoscine-N-butylbromide was needed in one patient each in groups 1 and 4. Serious complications related to peppermint oil did not occur. Inhibitory effect of peppermint appears to be identical to that of glucagon. CONCLUSION: Duodenal relaxation was obtained with 20 mL of 1.6% peppermint oil solution in the duodenum, but additional administration may be required. Peppermint oil is useful as an antispasmodic agent for ERCP.

Adult↗

Influence of peppermint oil on absorptive and secretory processes in rat small intestine.

BACKGROUND: Peppermint oil is used to relieve the symptoms of irritable bowel syndrome, relaxing intestinal smooth muscle by reducing the availability of calcium, but its effects on intestinal transport are unknown. AIMS: To determine the effect of peppermint oil on intestinal transport processes. METHODS: The influence of peppermint oil on intestinal transport was investigated in rat jejunum using both intestinal sheets mounted in Ussing chambers and brush border membrane vesicles. RESULTS: Mucosal peppermint oil (1 and 5 mg/ml) had no significant effect on basal short circuit current, but inhibited the increase associated with sodium dependent glucose absorption. The increased short circuit current induced by serosal acetylcholine, a reflection of calcium mediated electrogenic chloride secretion, was unaffected by mucosal peppermint oil (5 mg/ml). In contrast, serosal peppermint oil (1 mg/ml) inhibited the response to acetylcholine without reducing the effect of mucosal glucose. In brush border membrane vesicles active glucose uptake was inhibited by extravesicular peppermint oil at concentrations of 0.5 and 1 mg/ml. CONCLUSIONS: Peppermint oil in the intestinal lumen inhibits enterocyte glucose uptake via a direct action at the brush border membrane. Inhibition of secretion by serosal peppermint oil is consistent with a reduced availability of calcium.

Absorption↗

The mechanism of action of peppermint oil on gastrointestinal smooth muscle. An analysis using patch clamp electrophysiology and isolated tissue pharmacology in rabbit and guinea pig.

An investigation of the mechanism of peppermint oil action was performed using isolated pharmacological preparations from guinea pig large intestine and patch clamp electrophysiology techniques on rabbit jejunum. Peppermint oil relaxed carbachol-contracted guinea pig taenia coli (IC50, 22.1 micrograms/mL) and inhibited spontaneous activity in the guinea pig colon (IC50, 25.9 micrograms/mL) and rabbit jejunum (IC50, 15.2 micrograms/mL). Peppermint oil markedly attenuated contractile responses in the guinea pig taenia coli to acetylcholine, histamine, 5-hydroxytryptamine, and substance P. Peppermint oil reduced contractions evoked by potassium depolarization and calcium contractions evoked in depolarizing Krebs solutions in taenia coli. Potential-dependent calcium currents recorded using the whole cell clamp configuration in rabbit jejunum smooth muscle cells were inhibited by peppermint oil in a concentration-dependent manner. Peppermint oil both reduced peak current amplitude and increased the rate of current decay. The effect of peppermint oil resembled that of the dihydropyridine calcium antagonists. It is concluded that peppermint oil relaxes gastrointestinal smooth muscle by reducing calcium influx.

Animals↗

The actions of peppermint oil and menthol on calcium channel dependent processes in intestinal, neuronal and cardiac preparations.

The activities of menthol and peppermint oil were determined in guinea-pig ileal smooth muscle, in rat and guinea-pig atrial and papillary muscle, in rat brain synaptosomes and in chick retinal neurones by pharmacological 45Ca2+ uptake and radioligand binding assays. Menthol is a major constituent of peppermint oil and is approximately twice as potent as peppermint oil as an inhibitor of K+ depolarization-induced and electrically stimulated responses in ileum and electrically stimulated atrial and papillary muscles. IC50 values in the ileal preparation ranged from 7.7 to 28.1 micrograms ml-1 and in the cardiac preparations from 10.1 to 68.5 micrograms ml-1. Similar potencies were demonstrated against K+ depolarization-induced 45Ca2+ uptake in synaptosomes and against K+ depolarization and Bay K 8644-induced uptake in chick retinal neurons. IC50 values for menthol inhibition of K+ and Bay K 8644 responses in the retinal neurons were 1.1 x 10(-4) M (17.2 micrograms ml-1) and 1.75 x 10(-4) M (26.6 micrograms ml-1), respectively, and for peppermint oil were 20.3 and 41.7 micrograms ml-1 respectively. Both menthol and peppermint oil inhibited specific [3H]nitrendipine and [3H]PN 200-110 binding to smooth and cardiac muscle and neuronal preparations with potencies comparable to, but slightly lower than, those measured in the pharmacological and 45Ca2+ uptake experiments. Binding of menthol and peppermint oil, studied at 78 micrograms ml-1, was competitive against [3H]nitrendipine in both smooth muscle and synaptosome preparations. The data indicate that both menthol and peppermint oil exert Ca2+ channel blocking properties which may underlie their use in irritable bowel syndrome. Ca2+ channel antagonism may not be the only pharmacological effect of menthol and peppermint oil contributing to intestinal smooth muscle relaxation.

Animals↗

Evaluation of peppermint oil and ascorbyl palmitate as inhibitors of cytochrome P4503A4 activity in vitro and in vivo.

OBJECTIVES: Our study was designed to determine the effect of peppermint oil and ascorbyl palmitate on cytochrome P4503A4 (CYP3A4) activity in vitro and oral bioavailability of felodipine in humans. METHODS: Reversible and mechanism-based inhibitions of nifedipine oxidation were studied in human liver microsomes. The oral pharmacokinetics of felodipine and its dehydrofelodipine metabolite were determined in 12 healthy volunteers after administration of felodipine, 10-mg extended-release tablet, with grapefruit juice (300 mL), peppermint oil (600 mg), ascorbyl palmitate (500 mg), or water in a randomized 4-way crossover study. RESULTS: Peppermint oil (inhibition constant [K(i)] = 35.9 +/- 3.3 microg/mL, mean +/- SEM) and 2 constituents, menthol (K(i) = 87.0 +/- 7.0 micromol/L), and menthyl acetate (K(i) = 124.0 +/- 7.0 micromol/L), produced reversible inhibition of nifedipine oxidation. Ascorbyl palmitate was more potent (K(i) = 12.3 +/- 0.5 micromol/L). None of these substances were mechanism-based inhibitors. Grapefruit juice and peppermint oil increased the area under the curve (AUC) values of felodipine to 173% (range, 94%-280%; P <.01) and 140% (range, 77%-262%; P <.05), respectively, of those with water. They augmented the peak plasma concentration (C(max)) of felodipine and the AUC and C(max) of dehydrofelodipine but did not alter the half-life (t(1/2)) of either substance. Grapefruit juice decreased the dehydrofelodipine/felodipine AUC ratio, but peppermint oil did not. Ascorbyl palmitate did not change the pharmacokinetics of felodipine or dehydrofelodipine compared with water. CONCLUSIONS: Peppermint oil, menthol, menthyl acetate, and ascorbyl palmitate were moderately potent reversible inhibitors of in vitro CYP3A4 activity. Grapefruit juice increased the oral bioavailability of felodipine by inhibition of CYP3A4-mediated presystemic drug metabolism. Peppermint oil may also have acted by this mechanism. However, this requires further investigation. Ascorbyl palmitate did not inhibit CYP3A4 activity in vivo.

Administration, Oral↗

Peppermint oil reduces gastric spasm during upper endoscopy: a randomized, double-blind, double-dummy controlled trial.

BACKGROUND: GI endoscopy without general anesthesia causes a hyperperistaltic state in the stomach, which frequently necessitates the use of antispasmodic agents, such as hyoscine-N-butylbromide, but these drugs have side effects. Peppermint oil is harmless and acts locally to inhibit GI smooth muscle contraction. METHODS: A randomized double-blind, double-dummy, controlled trial was conducted in 100 patients to compare the antispasmodic effects of hyoscine-N-butylbromide administered intramuscularly and a placebo solution administered intraluminally by means of the endoscope, and also the effects of a placebo solution administered intramuscularly with those of a peppermint oil solution administered intraluminally. The percent change in diameter of the pyloric ring before and after the administrations was defined as the opening ratio, and the percent change in diameter between the maximally and minimally opened pyloric ring states was defined as the contraction ratio. Time until disappearance of the contraction ring(s) in the gastric antrum and side effects of the drugs were also determined. RESULTS: The opening ratio was significantly higher in the peppermint oil administration group than in the hyoscine-N-butylbromide injection group. The contraction ratio after peppermint oil administration was significantly lower than that after hyoscine-N-butylbromide injection. The time required for disappearance of the antral contraction ring(s) was shorter in the peppermint oil group (97.1 +/- 11.4) than in the hyoscine-N-butylbromide group (185.9 +/- 10.1 s; p < 0.0001). No significant side effects were associated with peppermint oil, whereas hyoscine-N-butylbromide injection produced side effects such as dry mouth, blurred vision, and urinary retention. CONCLUSIONS: Peppermint oil solution administered intraluminally can be used as an antispasmodic agent with superior efficacy and fewer side effects than hyoscine-N-butylbromide administered by intramuscular injection during upper endoscopy.

Adult↗

Peppermint oil improves the manometric findings in diffuse esophageal spasm.

BACKGROUND: Diffuse esophageal spasm (DES) is an uncommon condition that results in simultaneous esophageal contractions. Current medical treatment of DES is frequently unsatisfactory. We hypothesized that, as a smooth muscle relaxant, peppermint oil may improve the manometric findings in DES. STUDY: Eight consecutive patients with chest pain or dysphagia and who were found to have DES were enrolled during their diagnostic esophageal manometry. An eight-channel perfusion manometry system was used. Lower esophageal sphincter pressure and contractions of the esophageal body after 10 wet swallows were assessed before and 10 minutes after the ingestion of a solution containing five drops of peppermint oil in 10 mL of water. Each swallow was assessed for duration (seconds), amplitude (mm Hg), and proportion of simultaneous and multiphasic esophageal contractions. RESULTS: Lower esophageal sphincter pressures and contractile pressures and durations in both the upper and lower esophagus were no different before and after the peppermint oil. Peppermint oil completely eliminated simultaneous esophageal contractions in all patients (p < 0.01). The number of multiphasic, spontaneous, and missed contractions also improved. Because normal esophageal contractions are characteristically uniform in appearance, variability of esophageal contractions was compared before and after treatment. The variability of amplitude improved from 33.4 +/- 36.7 to 24.9 +/- 11.0 mm Hg (p < 0.05) after the peppermint oil. The variability for duration improved from 2.02 +/- 1.80 to 1.36 +/- 0.72 seconds (p < 0.01). Two of the eight patients had chest pain that resolved after the peppermint oil. CONCLUSIONS: This data demonstrates that peppermint oil improves the manometric features of DES.

Administration, Oral↗

Effect of peppermint oil and caraway oil on gastrointestinal motility in healthy volunteers: a pharmacodynamic study using simultaneous determination of gastric and gall-bladder emptying and orocaecal transit time.

BACKGROUND: Although peppermint oil and caraway oil are frequently used in herbal drugs for abdominal discomfort and pain, the pharmacological insights into their effects on the gastrointestinal tract are poor. METHODS: The pharmacodynamic effects of 90 mg peppermint oil (WS 1340) and 50 mg caraway oil (WS 1520) on the motility of the stomach and gall-bladder, and on the orocaecal transit time, in comparison with placebo, 10 mg cisapride and 10 mg n-butylscopolamine, were studied in 12 healthy volunteers. The study involved simultaneous ultrasonic determination of gastric and gall-bladder emptying, together with assessment of the orocaecal transit time using the lactulose H2 breath test. The combination of these methods allows three gastrointestinal organs to be studied in one subject simultaneously. RESULTS: The antral filling time was comparable with placebo, peppermint oil, caraway oil and cisapride, whereas it was significantly shortened (P = 0.04, two-sided paired t-test) with n-butylscopolamine. The gastric emptying time did not differ significantly between placebo, peppermint oil, caraway oil and cisapride, but was significantly prolonged by n-butylscopolamine (P = 0.04, two-sided paired t-test). Complete inhibition of gall-bladder emptying was caused by both oils and n-butylscopolamine. Cisapride significantly shortened gall-bladder emptying compared with placebo (P = 0.02, two-sided signed rank test). The orocaecal transit time was significantly prolonged by peppermint oil (P = 0.004) and n-butylscopolamine (P = 0.002), but not significantly prolonged by caraway oil (P = 0.06); it was significantly shortened by cisapride (P = 0.04, all two-sided paired t-test). CONCLUSIONS: Peppermint oil and caraway oil show a relaxing effect on the gall-bladder and the former slows small intestinal transit. Further studies should investigate the effects of both oils on a maximal contraction stimulus on the gall-bladder, and in patients suffering from motility disorders.

Adult↗

A combination of peppermint oil and caraway oil attenuates the post-inflammatory visceral hyperalgesia in a rat model.

OBJECTIVE: Visceral hyperalgesia plays a pivotal role in manifestation of symptoms in patients with functional gastrointestinal disorders. In clinical studies combined treatment of peppermint- and caraway oil significantly reduced symptoms. Thus, the aim of this study was to characterize the effects of peppermint- and caraway oil, individually and in combination, on visceral nociception in a rat model of post-inflammatory visceral hyperalgesia. MATERIAL AND METHODS: On day 28, male Lewis rats (n=80) were randomized to treatment with a rectal administration of trinitrobenzene sulphonic acid (TNBS)/ethanol or physiological saline solution. To quantify the visceromotor response to a standardized colorectal distension, bipolar electrodes were implanted into the external oblique musculature, just superior to the inguinal ligament for electromyographic recordings on day 3. On day 0, baseline measurement was performed. Thereafter, oral treatment with peppermint- or caraway oil or combination treatment was started and continued for 14 consecutive days. After 7 and 14 days of treatment a colorectal distension was performed. Colonic tissue samples were obtained on days 0, 7 and 14 to assess histological alterations due to the different treatment groups and the influence of different compounds. RESULTS: After a single instillation of TNBS/ethanol persistent elevation of the visceromotor response at all different time-points was observed, although colonic mucosa was completely normal. After 14 days of combined treatment with peppermint- and caraway oil, a reduced visceromotor response of up to 50% compared to placebo was detected in TNBS/ethanol pretreated animals. In contrast, neither peppermint- nor caraway oil had a significant effect on post-inflammatory visceral hyperalgesia. In saline-treated controls there was no significant difference in the visceromotor response. CONCLUSIONS: These data show that combined treatment with peppermint- and caraway oil modulates post-inflammatory visceral hyperalgesia synergistically. The exact mechanisms have to be further investigated.

Administration, Rectal↗

Exposure to airborne microorganisms, dust and endotoxin during processing of peppermint and chamomile herbs on farms.

The aim of this study was to determine the levels of microorganisms, dust and endotoxin in the air during processing of peppermint (Mentha piperita) and chamomile (Matricaria recutita) by herb farmers, and to examine the species composition of airborne microflora. Air samples were collected on glass fibre filters by use of personal samplers on 13 farms owned by herb cultivating farmers, located in Lublin province (eastern Poland). The concentrations of total viable microorganisms (bacteria + fungi) in the farm air during processing of peppermint herb were large, within a range from 895.1-6,015.8 x 10(3) cfu/m(3) (median 1,055.3 x 10(3) cfu/m(3)). During processing of chamomile herb they were much lower and varied within a range from 0.88-295.6 x 10(3) cfu/m(3) (median 27.3 x 10(3) cfu/m(3)). Gram-negative bacteria distinctly prevailed during processing of peppermint leaves, forming 46.4-88.5 % of the total airborne microflora. During processing of chamomile herb, Gram-negative bacteria were dominant at 3 out of 6 sampling sites forming 54.7-75.3 % of total microflora, whereas at the remaining 3 sites the most common were fungi forming 46.2-99.9 % of the total count. The species Pantoea agglomerans (synonyms: Erwinia herbicola, Enterobacter agglomerans ), having strong allergenic and endotoxic properties, distinctly prevailed among Gram-negative isolates. Among fungi, the most common species was Alternaria alternata. The concentrations of airborne dust and endotoxin determined on the examined herb farms were large. The concentrations of airborne dust during peppermint and chamomile processing ranged from 86.7-958.9 mg/m(3), and from 1.1-499.2 mg/m(3), respectively (medians 552.3 mg/m(3) and 12.3 mg/m(3)). The concentrations of airborne endotoxin determined during peppermint and chamomile processing were within a wide range 1.53-208.33 microg/m(3) and 0.005-2604.19 microg/m(3) respectively (medians 57.3 microg/m(3) and 0.96 microg/m(3)). In conclusion, farmers cultivating peppermint are exposed during processing of this herb to large concentrations of airborne microorganisms, dust and endotoxin posing a risk of work-related respiratory disease. The exposure to bioaerosols during processing of chamomile is lower; nevertheless, peak values create a respiratory risk for exposed farmers.

Agricultural Workers' Diseases↗

Qualitative and quantitative olfactometric evaluation of different concentrations of ethanol peppermint oil solutions.

Selection of an adequate placebo is a major problem in clinical trials of Euminz(R) (10% peppermint oil/ethanol) which is used topically for the treatment of tension-type headache. This randomized, controlled, double-blind, cross-over study was performed to investigate whether there are qualitative differences between 10%, 1%, 0.5%, 0.1%, and 0% peppermint oil. Forty-one healthy subjects participated (age range 21-28 years); they rated both intensity, and hedonic tone of the stimuli. Verbal descriptions were combined to multiple response sets (MRS). In addition, the trigeminal impact of odorants was determined. Intensity ratings and MRS "menthol like" and "alcohol/solvent" changed with stimulus concentration. However, intensity had no significant effect on hedonics, trigeminal impact, or the number of descriptive items used. When MRS "menthol like" and "alcohol/solvent" were analysed after being weighted with intensity ratings, changes in relation to stimulus concentration were lost. Thus, the differences between the five concentrations of peppermint oil were--to their largest part--due to changes in stimulus intensity. Considering the large day-to-day variability of olfactory sensitivity the present data support the hypothesis that the odour quality of 10% peppermint oil cannot be discriminated from the odour of 0.1%, 0.5%, or 1% peppermint oil when tested on separate days.

Adult↗

Preliminary investigation of the effect of peppermint oil on an objective measure of daytime sleepiness.

The assertion, often quoted in the popular literature, that peppermint has invigorating properties has been investigated through objective assessment of daytime sleepiness. Pupillary fatigue oscillations have been used to give an index of pupillary unrest that can be used as a reliable measure of daytime sleepiness. When compared with a no-odour condition, the presence of peppermint oil limited the increase in sleepiness during 11 min spent in a darkened room. This significant difference in sleepiness between the peppermint oil and the no-odour conditions was shown not to be related to differences in subjective ratings of initial sleepiness, from the Stanford Sleepiness Scale (SSS). Neither was it related to differences in initial pupillary unrest or mean pupil size. It seems that in conditions that favour an increase in daytime sleepiness, peppermint oil can indeed reduce sleepiness. However, the mechanisms by which peppermint oil has its effect and the applicability of these findings to situations in everyday life will require further empirical investigation.

Adult↗