Buzz
You’ve likely heard of castile soap (hello, Dr. Bronner's), but what exactly is it, and how does it differ from the other soaps available? Castile soap stands apart from your standard body wash and cleaning detergent for a variety of reasons, which is why it has become a staple in many households. If you're unfamiliar with this versatile soap or uncertain how to use it, we asked experts to share all the important details about this time-tested formula.
What Exactly Is Castile Soap?
Originating in the Castile region of Spain, castile soap is an oil-based cleanser that has been around for centuries. Initially crafted from olive oil, it has since evolved to include various vegetable oils in its formulation.
"While castile soap was traditionally made with olive oil, today it’s mostly created using coconut oil, which is more readily available and cost-effective," explains cosmetic chemist Kelly Dobos. Castile soap is primarily sold as a liquid, though bar versions are also available.
The best way to understand castile soap is to think of it as "true soap," created by the reaction of natural oils and fats with a base like sodium or potassium hydroxide. "Many people today use the word soap to describe various cleansing liquids and bars, including those primarily made with synthetic surfactants. What we often call 'soap' today is actually detergent—and detergents are not biodegradable," says Joshua Onysko, founder of Alpine Provisions. In contrast, castile soaps are naturally derived and, as such, they are biodegradable.
Dr BronnerUses of Castile Soap
What’s incredible about castile soap is its versatility. "Not only can castile soap be used to cleanse your body and hair, but it also serves as an all-purpose cleaner for household chores, laundry, and even for cleaning makeup brushes and sponges," says Dobos. "However, castile soap is quite concentrated and should be diluted before use." For instance, you can dilute it and place it in a soap dispenser.
Body Care Applications
Castile soap is perfect for all kinds of body care routines (we're fans of Alpine Provisions Castile Body Wash). Use it as a body wash in the shower, or as a face cleanser or makeup remover (just be aware it might be a bit drying compared to facial cleansers specifically designed for that purpose).
Some people even use castile soap for shaving and to clean oral care items like retainers and dentures. Some go so far as to brush their teeth with it, though it’s not necessarily recommended, and there’s no clear consensus on whether it's safe to do so.
Household Applications
Around the house, castile soap is ideal for washing everything from dishes to laundry and delicates. It can also be used as a window or toilet cleaner, for wiping down countertops, and even for mopping floors. This soap is often praised as a versatile all-purpose cleaner.
While castile soap is most commonly used inside the home, there are many creative ways people apply this ancient formula outdoors as well. For instance, "Diluted castile soap solutions can even be used in the garden to combat small, soft-bodied mites or aphids," says Dobos. "However, keep in mind that some plants, like tomatoes, are sensitive to soapy sprays, so a bit of research is necessary beforehand."
You can also set up a small dish with apple cider vinegar and soap to help eliminate fruit flies in your kitchen. "The vinegar lures the flies in, and the soap breaks the surface tension of the water, causing the bugs to slip in and be unable to escape," explains Dobos.
Advantages of Castile Soap
Castile soap is a gentle yet incredibly effective cleanser for the skin. Despite its ability to remove even the toughest dirt, it is also hydrating due to the saponified oils, ensuring that your skin won’t feel stripped or overly dry.
An added benefit for vegans: Castile soap is made entirely from vegetable fat, not animal fat. Additionally, since it’s a highly concentrated formula, you can use less soap, minimizing waste.
Onysko explains that castile soap's natural saponification process has been used for thousands of years, creating soap that not only protects us from germs and viruses but is also gentler on our bodies and the environment.
Drawbacks of Castile Soap
Since castile is a true soap, it has a higher pH, which can be drying and irritating with extended skin contact—such as when washing a sink full of dishes. If you experience any skin irritation, stop using the soap to avoid further issues.
"It doesn’t work as effectively in hard water and can leave deposits in tubs and showers, which eventually turn gray as dirt and scum accumulate," says Dobos. If you use castile soap frequently, be sure to clean the scum regularly, including the drains where it may build up.
