Oil of Oregano for Asthma

Oil of oregano itself has not been studied in asthma. What exists are two small trials of purified carvacrol, the compound that makes up most of oregano oil, given as capsules to adults with asthma for 2 months (Alavinezhad 2018; Ghorani 2021, Phytomedicine). In the larger trial they were taken on top of usual medicines.

Both reported better lung function tests and fewer respiratory symptoms with carvacrol and no change with placebo. They were small (23 and 33 people), came from the same Iranian research group, and mostly compared each group with its own starting point. That makes this early, promising data on carvacrol, not evidence that oregano oil helps asthma.

Earlier lab and animal studies reported that carvacrol relaxes tracheal (windpipe) smooth muscle and had a preventive effect in asthmatic animals, which is why it was tested in people (Alavinezhad 2018). In the human trials, carvacrol lowered hs-CRP and white blood cell counts and improved oxidative stress markers and cytokine levels (Alavinezhad 2018; Ghorani 2021, Phytomedicine).

In veterans with lung damage from sulfur mustard, FEV1 (the volume of air breathed out in one second) rose and TNF-alpha and other inflammatory markers fell in the carvacrol group compared with baseline (Khazdair 2019).

These are changes in blood markers and spirometry over 2 months. No trial counted asthma attacks, emergency visits or steroid courses, the outcomes that matter most in asthma.

Oregano oils contain roughly 68-82% carvacrol along with other compounds (Maral 2022), so a dose of oregano oil delivers a different and variable amount of carvacrol. The effects of pure carvacrol can't simply be assumed for oregano oil.

Both asthma trials used purified carvacrol at 1.2 mg per kg of body weight a day, about 84 mg for a 70 kg adult, for 2 months (Alavinezhad 2018). In the larger trial, the capsules were taken three times a day alongside routine asthma medicines (Ghorani 2021, Phytomedicine).

No trial has tested an oregano oil dose for asthma, and the carvacrol in a given oregano oil product depends on the plant species and processing.

In a double-blind, placebo-controlled phase II trial, 23 adults with asthma took carvacrol (1.2 mg/kg a day, n = 12) or placebo (n = 11) for 2 months. Lung function tests rose and most respiratory symptoms fell in the carvacrol group, along with total white cells and hs-CRP (p < .05 to p < .001); the placebo group did not change (Alavinezhad 2018).

A second double-blind trial in 33 adults with moderate asthma (17 carvacrol, 16 placebo) found the same pattern at 1 and 2 months, with improvements in oxidative stress markers and cytokines (Ghorani 2021, Phytomedicine). In both, most comparisons were against each group's own baseline rather than directly against placebo, which overstates certainty.

The same group tested carvacrol at the same dose in veterans with lung disorders from sulfur mustard exposure decades earlier. In 20 patients, FVC, peak expiratory flow and inflammatory and oxidant markers were significantly better than placebo after 2 months (Khazdair 2018). In 21 patients, FEV1 and wheeze and cough improved versus baseline (Khazdair 2019).

These support a respiratory effect of carvacrol, but sulfur mustard injury is a different disease from asthma.

No trial of oregano oil in asthma; no trial outside one research group; no trial longer than 2 months; and no counts of asthma attacks or rescue medicine use. The evidence is promising for carvacrol as a research compound and absent for oregano oil.

See our asthma page for the wider picture.

In a one-month phase I study in healthy adults, carvacrol at 1 and 2 mg/kg a day left all blood and urine tests within normal ranges, though some values such as prothrombin time and HDL cholesterol shifted (Ghorani 2021, Drug Chem Toxicol). Oregano is generally well tolerated, with stomach upset and allergic skin reactions reported rarely (LactMed).

For people with asthma, allergy matters most: systemic allergic reactions to oregano and thyme have been documented, with cross-sensitivity across mint-family herbs (Benito 1996).

In the larger asthma trial, carvacrol was given alongside routine asthma medicines (Ghorani 2021, Phytomedicine), but interactions were not formally studied. Prothrombin time rose in a carvacrol safety study, which matters if you take a blood thinner (Ghorani 2021, Drug Chem Toxicol).