The most powerful antisceptic honey so far discovered, Comvita offers extra strength Manuka with a guaranteed UMF (Unique Manuka Factor) of 10+, 15+, or 20+. This is a rating method that compares batches of honey with the antimicrobial potency of normal antiseptic. The Active 10+ has two and a half times the power of standard antiseptic. Factors 10+, 15+, 18+ and 20+ are effective used both internally or externally.