The European Commission has approved the administration of thyme for cough and bronchitis.(1) In the case of thymol and carvacrol, a broad spectrum of effects against bacteria involved in the infections of the upper respiratory tract has been observed. It is believed that thymol and carvacrol exert their antibacterial activity through complex formation with the proteins in the bacterial membrane. A synergistic effect has also been demonstrated for thymol and carvacrol. Furthermore, it has been demonstrated that sufficient doses of thymol and carvacrol have relaxant effects on trachea. Various clinical trials have confirmed the efficacy of thyme on productive cough. In a randomized double-blind clinical trial, 60 patients with productive cough were administered thyme syrup or bromhexine syrup for a period of 5 days. According to the patients’ self-reports, there existed no significant difference between the two groups and both observed identical improvement by both of the medications. There was significant non-statistical progress in health of non-smokers compared to smokers in both groups.(2)
In a study to evaluate the antibacterial properties of the essential oil of Iranian Thyme against standard strains of golden Staphylococcus, Escherichia coli, Streptococcus pyogenes, Streptococcus pneumonia, Proteus mirabilis and Bacillus cereus, it was demonstrated that this essential oil has desirable antibacterial effect against the mentioned microorganisms. The amount of MIC was reported from 0.39 mg/ml to 1.56 mg/ml, and the golden Staph was more sensitive than the other assessed bacteria (0.39 mg/ml). Streptococcus pyogenes (1.56 mg/ml) and Proteus mirabilis (1.56 mg/ml) were the most resistant. In the cases of Streptococcus pneumonia, Escherichia coli and Bacillus cereus, an identical MIC equal to 0.7 mg/ml was registered.(2)
In a study of the chemical compounds and anti-staphylococcus activity of the essential oil of Iranian thyme and its synergistic effect with vancomycin, it was demonstrated that the main components of this essential oil are thymol (38.7%), carvacrol (15.3%) and p-cymene (10.2%) and its MIC and MBC against the resistant and sensitive strains of the golden Staph to methicillin isolated from the clinic was reported as 0.25-1 and 0.5-2 μl/ml, respectively, and the essential oil demonstrated synergistic effects with vancomycin. The researchers came to the conclusion that Iranian thyme essential oil might be beneficial in control of infections caused by methicillin-resistant Staphylococcus aureus (MRSA).(2)
Commission E has approved the use of fennel for treatment of inflammation of mucus membranes in the upper respiratory tract. Fennel is expectorant and it enhances the mucociliary activity of the ciliated epithelium of the respiratory tracts. The chemical structure of the anethole present in fennel resembles that of catecholamines (adrenaline, noradrenaline and dopamine) and like adrenaline, fennel is a bronchodilator. In guinea pig, administration of fennel essential oil as inhaler caused mild antitussive or cough suppressant effects on coughs induced by mechanical stimulants. The antibacterial properties of fennel essential oil is determined as identical or more than the antibiotics streptopenicillin, penicillin and tetracycline.(2)
- Thyme and Fennel
To evaluate the effects of thyme and fennel essential oils in treatment of cough, in a controlled, randomized, double-blind clinical trial, 119 patients of more than 14 years of age suffering from acute cough were administered three times per day, 20 drops Tussivin Oral Drop (containing sweet fennel and Iranian thyme essential oils), clobutinol drop or placebo for 3 days. At the end of this course, complete recovery was reported in the group receiving Tussivin Oral Drop and clobutinol as 50% and in the placebo group 9.1%. The efficacy of Tussivin Oral Drop, clobutinol and placebo in patients with productive cough was reported as 66.7%, 55% and 14.3%, respectively and 56.5%, 55% and 20% in patients with nonproductive cough. Regrading the degree of improvement of cough, significant difference was observed between Tussivin Oral Drop, clobutinol and placebo (p<0.01), but no significant difference was observed between Tussivin Oral Drop and clobutinol (p>0.4).(4)
In another controlled, double-blind clinical trial, 62 patients with acute cough were randomly divided into two groups of Thymogel Oral Soft Capsule (containing essential oils of sweet fennel and Iranian thyme) or placebo, and were administered for 3 days, one soft capsule every 8 hours. After re-evaluation of the patients and gathering of data, the degree of recovery was calculated and to compare the treatment groups, chi-square test and Fisher’s exact test were used. The results from this study showed that after 72 hours, total alleviation of cough had occurred in 62.5% of the patients in the Thymogel Oral Soft Capsule group and 20% of the patients in the placebo group (p=0.008).(6) Considering the expectorant properties of fennel, alleviation of cough along with aiding of expectoration is a characteristic of Thymogel Oral Soft Capsule.