The dosage of oregano oil depends on both the method of taking the oil and the reason for using it. The recommended oral dosage for treating infections, parasites and gastrointestinal disorders, depending on the severity of the condition, is 200 to 500 mg taken three or four times daily.
If applied topically for nail fungus or other skin conditions, the oregano oil should be diluted with olive oil at the rate of 1 drop of oregano oil for 1 tablespoon of olive oil.
Oregano oil can also be used to combat respiratory, sinus, cold, and flu symptoms using steam inhalation. Add a few drops of oregano oil to a small pot of boiling water. While covering the head, place the face close to the pot and breath in the steam several times. Oregano oil should always be diluted with water or another type of oil for every method of use.