Caprylic acid is derived from coconut oil. It is a naturally occurring fatty acid that has been proven as an effective antifungal compound that kills candida yeast. K9 Yeast Defense combines caprylic acid with pau d’arco and oregano oil to optimize its anti-fungal and immune boosting properties. Pau d’arco and oregano are herbs that have been widely researched for their anti-microbial and anti-fungal properties.