Castile soap gets its name from the Castilian region of Spain, where it was first created thousands of years ago. “Prior to Castile soap, soap was always made with animal fats,” green living expert Lisa Bronner (yes, of Dr. Bronner’s fame) tells mindbodygreen. The legend goes that it was Spanish Monastics who first swapped sheep and beef fat out for olive oil to create the first vegetable-based soap all those years ago.
Nowadays, “Castile is truly a multipurpose soap and very popular amongst people who want to live a cleaner, healthier, and more natural life,” says Loni Brown, the founder and CEO of EntirelyEco. In addition to the original olive oil blend, you’ll also find solid and liquid Castile soaps make with coconut oil, palm kernel oil, hemp oil, or coconut oil. “The term is now used a little more generally for a vegetable-based soap,” says Bronner.