Historically Castile soap is a soap made with only three ingredients: olive oil, water and sodium hydroxide. The origin has been traced back to Castile, Spain and since olive oil does come from there that makes good sense. Other sources trace it to a little deeper into the Mediterranean regions of Europe such as Italy or Greece.
Today the term castile soap is beginning to take on new meaning. I have seen companies claim that they have a castile soap because it is made with all vegetable oils, not quite correct but it seems like it is becoming a more accepted norm as of late.
So why all the fuss? Well olive oil is great for you inside and out. Our skin's natural pH is 5.5 and conveniently olive oil's pH is also about 5.5 making it a good and gentle cleanser for just about anyone. I have heard it recommended to those with sensitive skin or conditioned skin as something that is mild and will leave skin feeling smooth and hydrated. Since this soap only has one oil it lacks some properties that other multi-oil soaps would have. For example, coconut oil helps to make soaps nice and hard and palm oil helps to make the bar last for a long time, castor oil (one of my favorite oils) helps to make soaps nice and bubbly. I am not saying that a castile bar cannot have these properties, it's just that the cure time is generally longer and it may not get as bubbly, or become as hard or last as long, but do not discount this soap. It's benefits far outweigh some of it's differences and a properly formulated bar should leave you feeling satisfied and wanting more.
Some soapmakers let their castile soaps cure for up to a year in order to have the properties that most people look for in a soap (a little bubbly and gently yet cleansing). That's just not for me but I see the appeal of a soap like this to some, it is simple and typically quite creamy and beautiful.
Until then, stay bubbly