Oregano leaf is likely safe when taken in the amounts found in food and possibly safe when taken by mouth or applied to the skin in medicinal amounts. Mild side effects include stomach upset. Oregano might also cause an allergic reaction in people who have an allergy to plants in the Lamiaceae family.
Not enough is known about the safety of using oregano oil in medicinal amounts.
Special Precautions & Warnings:
Pregnancy and breast-feeding: Oregano is possibly unsafe when taken by mouth in medicinal amounts during pregnancy. There is concern that oregano in amounts larger than food amounts might cause miscarriage. Not enough is known about the safety of oregano when used in medicinal amounts while nursing.
Bleeding disorders: Oregano might increase the risk of bleeding in people with bleeding disorders.
Allergies: Oregano can cause reactions in people allergic to Lamiaceae family plants, including basil, hyssop, lavender, marjoram, mint and sage.
Diabetes: Oregano might lower blood sugar levels. People with diabetes should use oregano cautiously.
Surgery: Oregano might increase the risk of bleeding. People who use oregano should stop 2 weeks prior to a scheduled surgery.