What Is Castile Soap, and How Can You Use It?

Castile soap has become a household staple for environmentally conscious cleaners everywhere. The soap can be used to lather up in the shower, or to clean away grit and grime all over the house and garden — but do you know what castile soap is, and what exactly makes it so versatile? Here’s everything you need to know.

Named after the olive oil-based soaps originating in Castile, Spain, castile soap can come in liquid or bar form, but it is made only from vegetable oils — i.e., no animal fats. Dr. Bronner’s, one of the most popular brands of castile soap, is primarily made of coconut, olive, and hemp oils, but other oils like avocado, almond, and walnut can also be used.

Like most soaps, which are on the more basic or alkaline side of the pH scale, castile soap registers at about 8.9 on the pH scale. This is around the same level as baking soda, and slightly more alkaline than mild dish soap, although less alkaline than bleach or corrosive tile cleaners.

Generally speaking, soap molecules (castile soap molecules included) have one end that is attracted to water, and another that avoids it. When soap is combined with water, it creates free-floating charged atoms that attract and capture dirt and other types of non-water-soluble molecules. And that’s how castile works, too.

This grease-grabbing quality makes castile soap useful on slick oven hoods, greasy pots and pans, and hard-to-clean oily spills — and really, pretty much everything else, too. Dr. Bronner marketed his castile soap for 18 uses (hence the famously long, wordy label detailing different ways to use it), but true devotees have found many more than those — but more on that below.

In addition to the aforementioned uses, castile soap and water can be used to clean counters, sinks, bathtubs, floors, or toilets; it can get rid of insects that infest houseplants, and can even replace laundry detergent. Outside of the kitchen, you can use it on your hair and body for a natural cleanse without artificial additives (as long as it’s diluted).

Because castile soap is biodegradable and nontoxic, it’s safe to use on pets, plants, on the skin and hair, and around kids. You can even clean vegetables with it, so long as it’s diluted enough — more on that belo. (Although it’s known as one of the safer cleansers, there are plenty of things you should never do with castile soap you can learn about here.)

As previously mentioned, castile soap needs to be diluted before using because it’s so strongly concentrated. Dr. Bronner’s general rule is to mix one part castile soap to 10 partsd water.

In addition to using it as a multi-purpose cleanser for the home and body, you can make it into liquid laundry soap, a DIY floor cleaner, and a simple foaming hand soap for your kitchen and bathroom. (Find plenty more uses for castile soap in the kitchen here.)

Additionally, don’t combine alkaline castile soap with an acid you might also use around the house like vinegar or lemon — the reaction cancels out the potency of both ingredients and can leave objects and surfaces with a white film that is difficult to remove.

You can buy castile soap at most drugstores, pharmacies, grocery stores, convenience stores, and online from places like Amazon or Walmart. Dr. Bronner’s has eight different scents of the “magic” soap, including unscented, for you to choose from.