We use three special preservatives all derived from natural ingredients such as aspen bark and fermented radish root (leucidal) and advise our customers to use within 6 months of opening for highest quality. Unopened products, that are not exposed to heat and high temperatures have a shelf life of approximately 18 months (although we have some batch samples that are still fresh and viable long past the 1 year mark.) We recommend storing our products in a cool, dry setting under 75 degrees F/ 24 degrees C to preserve their quality.