After two months of thyme consumption in our case group, the anti-inflammatory IL-4 level in the supernatant cell culture of PBMCs had a substantial decrease compared to the time before the treatment.
Extensive studies have been conducted on allergic rhinitis disorder, its symptoms and various treatments. Naturally, compounds are an important source for clinical proposes . In recent years, studies have been conducted on herbal medicines and their effects. For instance, many beneficial effects have been reported for the Shirazi thyme plant, and a number of them have been proven . As the role of cytokines is highlighted in many studies, it was attempted in the present study to evaluate the role of cytokines [12, 13]. In our previous study, the effects of Shirazi thyme consumption were evaluated on the clinical symptoms and severity of allergic rhinitis according to the SNOT22 questionnaire. We observed that the severity of the clinical symptoms in both case and control groups was improved after the treatment compared to the time prior to the treatment. Nevertheless, the severity of the clinical symptoms in the case group was dramatically greater after the treatment in contrast to the time before the treatment .
Studies have shown that the IL-4 cytokine, despite producing IgE that enhances allergy, can also produce IgG4, which is a blocking antibody and plays the role of anti-inflammatory cytokines. Likewise, the IL-5 level, an eosinophil recruitment cytokine, decreased in the supernatant cell culture of PBMCs after the course of treatment compared to the previous time in both groups. Regarding the fact that the level of IL-5 cytokine in the supernatant cell culture of PBMCs within the case group was higher before the start of treatment, the effect of thyme on decreasing its level was more likely than the control group . Therefore, these two findings (the increase in IL-4 and the decrease in IL-5) are consistent with the findings of studies showing the effects of Shirazi thyme consumption on the clinical symptoms. Moreover, the allergic rhinitis severity was evaluated according to the SNOT22 questionnaire. The severity of the clinical symptoms in both groups was better after the treatment in comparison with the before time. Nevertheless, the severity of the clinical symptoms in the case group was dramatically greater by the treatment. Similarly, the effects of the ZM syrup were evaluated on the gene expression rate in PBMC cells in the allergic rhinitis patients. The results presented that the TGF-β gene expression had no change in the control group and a slight decrease in the case group. The IL-10 gene expression also decreased in both control and case groups, although this reduction was more significant in the case group. The IL-17 gene expression decreased in the both groups, while it was significant only in the case group. Further, the FOXP3 gene expression decreased in both control and case groups, though it was more significant in the case group. They illustrated that IL-4 cytokines caused damage to Th17 cells. These cells are producers of IL-17 inflammatory cytokines . Accordingly, an increase in IL-4 in our study confirms with the reduced IL-17 in our previous study .
It was also demonstrated that the Thymol extract, the Flavonoid extract and the essence of this herb contained anti-inflammatory effects. In applying the administered dose, there was no significant difference in the anti-inflammatory effects of different fractions of the Shirazi thyme with the standard group receiving dexamethasone . Moreover, it became clear that the prevention of scar formation was another effect of the Shirazi thyme herb, which can be used as an anti-inflammatory drug in the future by extracting its effective substances [17, 18]. Due to the fact that IL-4 is an anti-inflammatory cytokine, by demonstrating the augmentation of IL-4 in patients consuming thyme, our study is probably able to confirm its anti-inflammatory effects.
A study was conducted in 2015 on the effects of the Shirazi thyme and the carvacrol compounds on inflammatory pulmonary changes and oxidative stress in guinea pigs suffering from COPD due to their exposure to cigarette smoke. The effect of this medicine was evaluated on blood cell total count, eosinophils, neutrophils count demonstrated in groups treated with dexamethasone, two high concentrations of the Shirazi thyme, and two concentrations of carvacrol. Changes toward recovery were observed dramatically. Dissimilar results in the control group was significant indicating the protective effects of the Shirazi thyme extract and its active ingredients, including carvacrol .
Other investigations on guinea pig groups were conducted to evaluate the effect of the Shirazi thyme on the responsiveness of the trachea in the pathologic lung. Their results illustrated that the groups afflicted with COPD had a significant improvement compared to the control group .
Emphysema in the group under treatment with the highest thyme and carvacrol concentrations had improved significantly compared to the group of patients without the treatment. Moreover, an almost equal effect was achieved by the Shirazi thyme compared to the effect of Dexamethasone. Furthermore, the anti-inflammatory effects of this herb were observed in our study. Based on its effect on a number of cytokines, they are the most important mediators of the immune system responses.
In addition, a study was conducted in 2011 on the effects of another herbal product (silymarin) on the treatment of chronic allergic rhinitis. The results clarified that the severity of the clinical symptoms of allergic rhinitis after the treatment with silymarins had a significant improvement, compared to the placebo group. The cytokines’s (IFN-γ, IL-4, and IL-5) serum levels did not significantly differ between the case and control groups after the treatment . Accordingly, the finding of the mentioned study does not match the variations of cytokines in our study. It can be explained by different study durations. Their study took one month, whereas our study lasted for two months. It is notable that a longer duration of medication provided a better effect on the immune system.
Overall, due to the proven effects of the Shirazi thyme herb on the treatment of inflammatory diseases and its availability in Iran, the consumption of this relatively safe herb (according to our study and other studies) is recommended. It is effective for inflammatory disorders, especially allergic rhinitis alongside the other treatments so as to further control patients’ symptoms. Moreover, due to the impact of the Shirazi thyme on the improvement of patients’ clinical symptoms, it is suggested to study the total and specific IgE level, and the number of eosinophils in the nasal mucosa on a significant number of patients. In addition, the clinical symptoms and previous cytokine levels should be observed.