The essential oil coming from the Manuka tree native to New Zealand. It is distantly related to the Australian Tea Tree Oil, although their chemical composition is very different.
The main antibacterial active in tea tree oil is terpinen-4-ol (40%), while manuka's main actives are so-called cyclic triketones, such as Leptospermone, Iso-leptospermone, and Flavesone (20-30%). Both oils are antibacterial and antifungal but in different ways.
While tea tree oil is a pretty well established anti-acne ingredient, manuka has more of a "might be useful" status for problem skin. Its strong suit is treating fungal infections such as athlete's foot, nail bed infections or foot odor. Other than that, manuka can help to relax muscles (useful for treating muscle and joint pain) and also has some antioxidant activity.
Show me some proof
- Christoph, F., K-H. Kubeczka, and E. Stahl-Biskup. "The composition of commercial manuka oils from New Zealand." Journal of Essential Oil Research 11.6 (1999): 705-710.
- Lis‐Balchin, M., S. L. Hart, and S. G. Deans. "Pharmacological and antimicrobial studies on different tea‐tree oils (Melaleuca alternifolia, Leptospermum scoparium or Manuka and Kunzea ericoides or Kanuka), originating in Australia and New Zealand." Phytotherapy Research 14.8 (2000): 623-629.