Editor's Note
Carvacrol is a monoterpene constituent of many plant essential oils including thyme and oregano. Carvacrol has been studied for effects on inflammatory mediators and lung pathology in animal models of pulmonary diseases. This randomized, placebo-controlled double-blind, clinical trial evaluated carvacrol effects on respiratory symptoms, pulmonary function tests (PFT), oxidative stress markers and cytokine levels in asthmatic patients. Thirty-three moderate asthmatic patients were divided to the two groups, placebo group (n = 16) and carvacrol group (1.2 mg/kg/day, n = 17); capsules were taken 3 times/day for two months, with respiratory symptoms, PFT, and oxidative stress markers evaluated before the treatment and at one and two months.
 
In the carvacrol group, respiratory symptoms significantly decreased after one- and two-month treatment, PFT values were significantly increased; most oxidative stress markers were improved following carvacrol treatment. Treatment with carvacrol for two‐month also significantly improved cytokine levels. No significant changes were observed in the above-noted parameters in the placebo group. The researchers conclude carvacrol has potential as a therapy for asthma and suggest further clinical research. 
Abstract

Background
Carvacrol effects on inflammatory mediators, lung pathology and tracheal responsiveness were indicated in animal models of pulmonary diseases.

Purpose
To evaluate carvacrol effects on respiratory symptoms, pulmonary function tests (PFT), oxidative stress markers and cytokine levels in asthmatic patients.

Study Design
This study was a randomized, placebo-controlled double-blind, clinical trial.

Methods
Thirty-three moderate asthmatic patients were divided to the two groups of: placebo group (n = 16) and carvacrol group (1.2 mg/kg/day, n = 17). Prepared capsules were taken for two months along, 3 times/day along with routine medications. Respiratory symptoms, PFT, and oxidative stress markers were evaluated before the treatment (step 0), and one (step I) and two months (step II) after the beginning of the treatment. However, cytokine levels in serum and supernatant of peripheral blood mononuclear cells (PBMC), and their gene expression were evaluated in step 0 and II.

Results
In carvacrol-treated group, respiratory symptoms significantly decreased after one- and two-month treatment with carvacrol compared to pre-treatment values (p < 0.05 to p < 0.001). Compared to step 0, PFT values were significantly increased in step I and II, in treated group with carvacrol (p < 0.05 to p < 0.001). Most oxidative stress markers were improved following carvacrol treatment (p < 0.05 to p < 0.001). Treatment with carvacrol for two‐month also significantly improved cytokine levels in serum and supernatant of PBMC, compared to step 0 (p < 0.05 to p < 0.001). However, no significant changes were observed in the above-noted parameters in the placebo group.

Conclusion
Due to anti-inflammatory and antioxidant effect, carvacrol could be suggested as a therapeutic agent for asthma.
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