Scientific studies show that oregano causes immediate relief in the Upper Respiratory
Many people report that the oregano plant helps them when they suffer from a virus and various symptoms like sore throat. Indeed, previous studies have shown that oregano has antiviral and antibacterial properties (see, for example, references 2 and 3 in the bibliography). But it is very difficult to know whether oregano is the cause that alleviates pain because it is possible that these symptoms would have dissipated anyway, with or without oregano consumption, due to the body's immune system. Therefore, the results of the study published in the journal Evidence-Based Complementary and Alternative Medicine in 2011 are extremely important.
The study conducted a randomized controlled trial. It compared an experimental group that received the oregano plant as the most dominant ingredient in a plant mixture to a control group that received only a placebo. Both groups received the exact same dose of either the treatment or the placebo—five times a day for three days. Thus, the study was able to identify and measure the causal effect of oregano.
If in both groups the sore throat and the rest of the symptoms were equally transient, the researchers would have concluded that the herbal mixture had no effect at all. But the results of the study showed otherwise: subjects in the experimental group reported relief of sore throat, hoarseness, or cough almost immediately, about twenty minutes after receiving treatment. After three days there was also a substantial improvement among the control group that did not consume the oregano plant, so the differences between the two groups were significantly reduced and almost disappeared. But the subjects who received the oregano treatment reported very significant relief in their condition almost immediately. Moreover, another set of results showed that the relief effect was more substantial and statistically significant for a subset of subjects who suffered from the most severe symptoms.
 Ben-Arye, E., Dudai, N., Eini, A., Torem, M., Schiff, E. and Rakover, Y., 2011. Treatment of upper respiratory tract infections in primary care: a randomized study using aromatic herbs. Evidence-based complementary and alternative medicine, 2011.
 M. H. Alma, A. Mavi, A. Yildirim, M. Digrak, and T. Hirata, “Screening chemical composition and in vitro antioxidant and antimicrobial activities of the essential oils from Origanum syriacum L. growing in Turkey,” Biological and Pharmaceutical Bulletin, vol. 26, no. 12, pp. 1725–1729, 2003.
 S. Soylu, H. Yigitbas, E. M. Soylu, and S¸ . Kurt, “Antifungal effects of essential oils from oregano and fennel on Sclerotinia sclerotiorum,” Journal of Journal of Applied Microbiology, vol. 103, no. 4, pp. 1021–1030, 2007.