What is the strongest natural antimicrobial?

There is no single strongest natural antimicrobial that works against all microbes for all people, but several natural substances have strong broad-spectrum antimicrobial activity demonstrated in laboratory studies, with honey, particularly Manuka honey, often considered among the strongest natural antimicrobials. Manuka honey from New Zealand has high methylglyoxal content and produces hydrogen peroxide, killing bacteria, including MRSA, by damaging cell walls and preventing biofilm formation, and is actually FDA approved for wound dressings. Other very strong natural antimicrobials include garlic which contains allicin that kills bacteria, viruses, and fungi, oregano oil containing carvacrol and thymol which are potent against bacteria and fungi, tea tree oil effective against bacteria and fungi including acne and athlete's foot, and colloidal silver which has historical use but safety concerns. Grapefruit seed extract, coconut oil containing lauric acid, and propolis from bees also show strong activity. However, strongest in lab does not mean safe or effective inside the body, concentration matters, and natural does not mean without side effects, essential oils can irritate skin and lungs if inhaled in high concentrations, especially in closed rooms. For indoor air, natural antimicrobials cannot replace HEPA filtration and proper ventilation for removing airborne microbes. For serious bacterial infections, natural antimicrobials are not substitutes for prescription antibiotics, which are dosed and proven to kill infections fast, and self-treating with natural agents can allow infections to worsen.