What Is Castile Soap?
Castile soap originated from the Castile region of Spain. Traditionally, Castile soap referred to a gentle soap made from 100% olive oil. Given that it originated in one of the world's most famous olive-growing regions, this makes perfect sense.
Today, soaps based primarily on olive oil but blended with other nourishing oils such as coconut oil, jojoba oil, or shea butter are more accurately known as Bastille soaps.
Why Dr Watkins Essentials Castile Soap Is Technically a Bastille Soap
Technically speaking, Dr Watkins Essentials Castile Soap is a Bastille soap, comprising 60% olive oil and 40% coconut oil.
I have included coconut oil because it produces a richer lather, making the soap more effective for stain removal and household cleaning. The trade-off is that it is marginally less hypoallergenic than a pure olive oil soap.
It is also worth checking the ingredient list of any liquid "Castile Soap" you purchase. Some products marketed as Castile soap contain palm oil as their primary ingredient. If you would like to know why I never use palm oil in my formulations, have a read of my blog on palm oil. My reasons extend well beyond its environmental impact.
Why I Love Castile Soap
Castile soap is one of the gentlest and most versatile cleansers available. If you have highly sensitive skin and struggle with conventional soaps, simply pour it neat into a foaming dispenser and you instantly have a luxurious liquid hand wash free from unnecessary additives and harsh detergents.
What's Really in Most Liquid Hand Soaps?
The next time you're in the supermarket—or even browsing luxury skincare brands—take a closer look at the ingredient list.
Chances are you'll find a sulphate-based detergent near the top.
Understanding Sulphate-Based Detergents
Common examples include:
- Sodium Dodecyl Sulphate (SDS)
- Sodium Lauryl Sulphate (SLS)
- Sodium Laureth Sulphate (SLES)
These detergents are highly effective cleansers but can also be extremely drying and irritating to the skin and scalp. For some people, they may contribute to irritation, cracking, eczema flare-ups, and sensitivity.
Of the three, SLES is generally considered the mildest, while SDS is the most aggressive.
During my years working in research laboratories, SDS powder was handled exclusively within fume hoods because inhaling the dust can be highly irritating to the respiratory system.
Are "Natural" Sulphates Any Better?
Some natural cleaning products replace SLS and SLES with Sodium Coco Sulphate (SCS), which is derived from coconut oil.
While SCS is often marketed as gentler, it still contains high levels of lauric acid derivatives that are converted into sulphated detergents during manufacturing.
By contrast, the saponification of olive and coconut oils produces a far simpler mixture:
- Sodium olivate
- Sodium cocoate
- Glycerol
- Water
(Liquid Castile soap contains the potassium forms of these soap molecules.)
The result is a cleanser that is remarkably gentle while still being highly effective.
The Many Uses of Castile Soap
One of the reasons I love Castile soap so much is its versatility.
Luxury Hand Wash
We've already mentioned the simplest hand wash imaginable.
For a more luxurious version, combine Castile soap with approximately 50% glycerol and add your favourite essential oils. My personal favourite blend is rose geranium and mānuka.
Laundry Liquid
Castile soap forms the base of my laundry liquid.
Because it cleans gently without stripping natural fibres, many people find they no longer need fabric conditioners, which are often packed with unnecessary chemicals.
Multi-Purpose Cleaner
I also use Castile soap as the detergent base in my multi-purpose cleaner.
It effectively removes dirt and grease while being significantly gentler on both your skin and the environment.
Household Cleaning Applications
Cleaning Range Hood Filters
Instead of running extractor fan filters through the dishwasher, soak them in hot water with a generous splash of Castile soap for around 30 minutes. The accumulated grease lifts away remarkably well.
Floor Cleaning
Simply dilute Castile soap in warm water to create an effective floor cleaner that leaves no harsh chemical odours behind.
Toilet Cleaning
A small amount of neat Castile soap can be used as an alternative to bleach-based toilet cleaners.
Soap is highly effective at removing dirt, grease, and many microorganisms, without the overpowering smell of conventional cleaners.
An Excellent Natural Stain Remover
My daughter recently discovered acrylic painting, which has inevitably led to a few clothing disasters.
For paint stains, simply:
- Dampen the stained area.
- Apply neat Castile soap.
- Scrub gently with a toothbrush or cleaning brush.
- Wash as normal.
Even stubborn blue and purple acrylic paint stains can be removed surprisingly effectively.
Gentle Enough for Precious Items
We have also used Castile soap to clean Lambie—the much-loved stuffed toy that accompanies my daughter everywhere.
By dampening the fabric, applying a small amount of Castile soap, and gently rubbing the surface, Lambie emerges looking clean, fresh, and almost new again.
DIY Cream Cleaner
Castile soap can also be used as the base for a homemade cream cleaner that smells significantly better than most commercial alternatives and is kinder to your skin.
Can You Use Castile Soap as Dishwashing Liquid?
Absolutely.
While Castile soap doesn't produce the towering bubbles many people associate with dishwashing liquids, it still cuts through grease effectively.
The truth is that bubbles are largely a marketing tool. The microscopic detergent structures known as micelles are what actually surround and lift grease and dirt away—whether large visible bubbles are present or not.
Simplify Your Cleaning Routine
Instead of purchasing separate laundry liquid, stain remover, dish soap, toilet cleaner, and floor cleaner, consider keeping a bottle of Castile soap on hand.
Its versatility allows you to replace multiple products with one simple formulation, reducing unnecessary chemicals in your home while maintaining excellent cleaning performance.
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