Published in the Caspian Journal of Internal Medicine, the study involved 84 med-school students between the ages of 18 and 24. Each subject was randomly assigned either ibuprofen, thyme oil, or a placebo to treat symptoms of dysmenorrhea, or menstrual cramps. Before receiving treatment, the groups reported average pain levels of 5.3, 6.5, and 6.2, respectively (on a scale of one to 10). In order to ensure the validity of the results, each group was given both capsules and drops of oil, but the thyme-oil group's capsules were placebos, while the ibuprofen group got placebo oil drops; the placebo group, of course, received both placebo capsules and placebo drops.
Each group received their treatment every six hours and recorded their pain levels one hour after each dose. The researchers found that the thyme-oil group reported an average pain level of 1.2 after treatment, while the ibuprofen group rated their pain at 1.5; the placebo group had an average pain level of 3.5.
Admittedly, this is a pretty small study, and the authors point out that the difference between the reduction in pain levels by the two medications wasn't statistically significant. So, while thyme oil may not be more effective than ibuprofen at treating menstrual cramps, it does seem to be an equally powerful alternative — and one with fewer potential side effects.