ZULU's Guardian Technology is an FDA and EPA approved antimicrobial additive that inhibits mold and bacterial growth to keep silicone food-contact surfaces cleaner. Guardian's antimicrobial additive is a specific proprietary solution which is infused into our silicone during the manufacturing process, and has the ability to inhibit the growth of microorganisms (like bacteria, mold and mildew) throughout the useful life of the product. This keeps the bottle fresher and cleaner for longer, and fights against product-damaging microbes that can quicken its deterioration. Our antimicrobial additive does not wash off or wear away, and will continually fight against potentially harmful bacteria that makes contact with the surface of the product.