What Is Castile Soap? Here’s Why You Need it in Your Home…

March 26, 2019

Castile soap is one of the oldest known soaps, yet continues to innovate the way we clean our homes today! You can use this simple all-natural soap to clean nearly anything in your home!

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Bottles of Castile soap in Laundry room.

A few years ago, I swapped all of our hand soap for a homemade hand soap recipe made with Castile soap.

I had seen Castile soap many times for sale in the grocery store, but I wasn’t really sure what it was. I decided to give it a try…and I haven’t looked back since!

Castile soap is one of my favorite green cleaning products. In fact, it’s one of the only things I use on a daily basis to keep our house and our bodies clean!

It can be used for so many things including: shampoo, body wash, hand soap, countertop cleaner, dish soap…and much more.

I use Castile soap as dishwashing soap, laundry detergent, hand soap, countertop spray, and soft scrub on a daily basis, but the uses are endless!

This magical green cleaning product is non-toxic and bio-degradable since it is made from plant-based oils rather than animal fat.

The most common brand is Dr. Bronner’s. You can typically find at your grocery store, but it is also available on Amazon and other online retailers. I have found that Target has the best price, Amazon sometimes offers it on sale, and if you can find it at Grocery Outlet, you’ll get a major deal!

It’s important to note: Castile soap comes in a concentrated form, and needs to be diluted in order to use! Follow the dilution suggestions on the bottle for everyday household uses.



What is Castile Soap?

Castile Soap is a plant based soap made from vegetable oil such as olive, coconut, palm, or any other plant based oil rather than from animal fat.

The soap is made by mixing potassium hydroxide lye with vegetable oil and purified water to create a liquid soap mixture.

Historically, this soap is made using only olive oil; however, modern brands like Dr. Bronner’s often add other vegetable oils such as coconut. The most important thing to remember is that this soap does not use any animal fat or animal byproducts to be made. 

If you would like to make your own Castile soap, you absolutely can! You’ll need Potassium hydroxide lye, coconut + olive oil, and distilled water! Of course making your own soap is a bit time consuming and requires some science, so purchasing it is a bit easier! 

The History of Castile Soap:

It is believed that Castile soap originated in the 11th C in Aleppo of the Levant region and moved westward after the first crusades.

When soap was discovered by Europeans after the first crusades, it became popular as it began revolutionizing hygiene.

The crusaders had witnessed how the soap was made during their time spent in the Holy Lands, and attempted to reproduce it.

Eventually the process made its way to Spain, and while most regions failed at reproducing the high-quality soap, one area in particular was able to get the recipe just right: Castile.

The soap being made in Castile became known for its superiority and became popular with Spanish royalty, which then spread to royalty in other countries.

Originally, the soap was made with laurel oil (bay leaves), but due to laurel oil being inaccessible in Spain, olive oil began being used, which was available in abundance.

It is believed that Castile soap reached England sometime between 1567 and 1616 and was known by its latin names: sapo hispaniensis (Spanish soap) or of sapo castilliensis (Castilian soap).

In the 17th C, Castile soap became controversial due to its Spanish Catholic ties. During the rein of Charles I, Spanish soap manufacturers purchased the monopoly of soap making; however, Protestant England did not approve of the monopoly of a Catholic manufacturer.

Ultimately the Spanish manufacturers lost the monopoly after campaigns of wash women showcasing local soaps being superior to Castile soap.

Castile soap is one of the oldest known soaps, yet continues to innovate the way we clean our homes today! You can use this simple all-natural soap to clean nearly anything in your home!
Click here for my recipe for homemade liquid hand soap!

How is Castile soap made?

Castile soap was originally made using Laurel (bay leaf) oil and lye (ash); however, as it spread through Europe where Laurel oil was unavailable, olive oil began being used.

It is made by combining lye, also known as caustic soda which is the common name for sodium hydroxide (for hard soaps) or potassium hydroxide (for liquid soaps), plant-based oil, and water.

Lye is highly soluble in water and produces caustic basic solutions. Lye is known for its cleaning abilities and is a common ingredient in oven cleaners and drain unclogging solutions due to its natural degreasing abilities!

When lye is mixed with fat or oil, soap is formed! Castile soap is made by combining lye with any type of vegetable or plant-based oil such as avocado, nut/seed, olive (most common), or hemp, among others.

The mixture produces a liquid soap that can be used to clean pretty much anything and everything! In modern day brands, the combination of olive oil & coconut oil is perfect for cutting grease without drying the skin!

What can Castile soap be used for?

Castile soap is one of the most incredible soaps because it can be used for practically anything you need to clean! Even your teeth or vegetables!

One of the most commonly available brands is Dr. Bronners. This soap comes in a concentrated form, so all you have to do is dilute it to suit your cleaning need!

Dr. Bronner’s dilution cheat sheet is a wonderful asset as you get started using Castile, but eventually you’ll know just how much (or how little) to use for your cleaning routines.

Castile soap is one of the oldest known soaps, yet continues to innovate the way we clean our homes today! You can use this simple all-natural soap to clean nearly anything in your home!

Examples of things it can be used for:

  • Shampoo (make sure to use acidic conditioner)
  • Vegetable Rinse
  • Laundry Soap
  • Dish Soap (hand washing only – not for dishwasher)
  • Liquid Hand Soap
  • Dog Shampoo
  • Countertop Spray
  • Mopping Solution
  • Toilet Bowl Cleaner
  • Shower & Tub Cleaner
  • Bath Soap
  • Facial Soap
  • Shaving Soap
  • Plant Spray for Bugs
  • Window Spray
  • Soft Scrub Cleaner

This is just the tip of the iceberg, you can pretty much clean anything in your home with this natural, bio-degradable soap!


Amazing Castile Soap uses!

click below to get the recipe for homemade dog shampoo as seen on Martha Stewart

How to dilute it:

Castile soap comes in a concentrated form and will always need to be diluted before using. Common dilutions are about 1/4 cup soap to 3-4 cups water for hand soap and dish soap.

I add about 1/4 cup to my laundry (in the normal soap dispenser). For dilution directions, see Dr. Bronner’s Dilution cheat sheet. I do not add the vinegar rinse as recommended on the bottle.

If you mix your own liquid hand soap and find that it is not sudsing enough, just add a little more soap to the mixture. I honestly eye-ball my measurements.

Castile Soap FAQ

Does Castile soap get sudsy?

Yes, this soap will suds up just like your traditional dish or hand soap. If it isn't sudsing up, you've probably diluted it too much. It doesn't need to suds up to be effective though!

Can I use the scented soap on my dishes?

Yes, I use lavender scented Castile soap for my laundry, dishes, and hands. I do not notice any scent left behind. You can purchase unscented if you do not like the smell.

Is Castile soap anti-bacterial?

Castile soaps work by attaching to dirt and germs and rinsing them away, leaving behind a clean surface.

Adding tea tree oil, which is a natural antibacterial oil, can help make your solution antibacterial, but please note, tea tree oil is toxic to cats.

Is this soap bio-degradable and non-toxic?

Pure Castile soaps are completely bio-degradable and non-toxic. Made with simple, age-old ingredients, you can even use pure Castile soap as a vegetable wash (diluted properly). This makes it safe for your self, your kids, and your pets (including dogs)!

Where can I buy it?

You can find Castile at most grocery stores! This makes it so convenient! You can also purchase it from Amazon or Dr. Bronner’s website.

What can I mix Castile soap with to create green cleaning products?

Castile soap doesn’t need to be mixed with much. In fact mixing it with common green cleaners can actually reverse the cleaning properties of the soap.

Since it is alkaline, do not mix it with vinegar. You will be left with a filmy mess!

Castile soap and baking soda share a similar pH level, and mixing the two together is safe. One of my favorite ways to use this soap is to sprinkle baking soda and a few drops of Castile and water over a dirty surface to create a soft scrub that works like magic! This is how I clean my farm sink when it gets disgusting!

Essential oils in Castile soap:

In addition to lye and oil, essential oils can be added to the soap for fragrance and additional cleaning properties. Dr. Bronner’s soap contains 2% essential oil making it safe for pets and household cleaning (including dishes / vegetable wash).

I’m noticing a film left on glass:

If you notice a film left on glass items after using Castile soap, you can use a diluted vinegar rinse. It’s important to use a vinegar rinse after using the soap. Do not mix vinegar and Castile soap together in the same solution, you will be left with a gunky mess.

When vinegar – an acid – is mixed with Castile soap – a base – they react together which causes the soap to un-saponify. Meaning the soap is reversed back to its original oil base, leaving you with nothing more than oil.

Instead, use this soap as you normally would to clean, then after (if needed) you can use a vinegar rinse. After washing dishes, dip them in a sink full of diluted vinegar and rinse. Or, after cleaning a tub or sink, spray a diluted vinegar spray, give a quick scrub, and rinse. The vinegar dissolves the soap scum build-up from leftover minerals that have reacted with the Castile soap.

Note: I have noticed that if I soak glassware in Castile soap, I am left with a thick film. To get rid of this film, I soak in a diluted vinegar rinse. Remember, it is not safe for dishwashers – so use it for hand washing dishes only!

How to use Castile soap for laundry:

I use Castile soap for all of our laundry. It works wonderfully! For spot treatment, I’m still a fan of Shout! however, I am on the hunt for a good all-natural spot remover.

To use your soap in your washing machine, simply treat it the same way you would normal detergent. I use anywhere from 1/4 cup to 1/2 cup of Castile soap per load. The rose and lavender scents are my favorite and leave our clothes, sheets, and towels smelling wonderful!

On the bottle of Dr. Bronner’s soap, you’ll see that it’s advised to add vinegar to the rinse cycle of your laundry. I do not do this simply because I don’t want to sit and wait to catch the rinse cycle to add the vinegar. Remember, don’t mix vinegar and Castile soap together. Instead, for laundry, I haven’t found vinegar to be necessary. I do not notice any filmy build-up on our clothing.

Castile soap is one of the oldest known soaps, yet continues to innovate the way we clean our homes today! You can use this simple all-natural soap to clean nearly anything in your home!

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  1. If you are looking for a great green spot cleaner I am now an avid user of puracy stain remover. The baby one or the regular both work great. I used to use oxyclean for my white slip covers and I hated the toxic smell but now I am fully satisfied with theirs! They sell that at target as well.

  2. Hi Chloe, my husband and I wish we could take advantage of the benefits of Castile soap. Unfortunately in our case, we are both skin-sensitive to it. My husband literally breaks out in hives from it.

    I mention this here because while we all want to be more health and planet conscious, not everyone can use all of the eco-friendly products available. Skin and other sensitivities can come into play. It’s more about finding which combination of natural products and ingredients works best for each individual.

    Cheers, Ardith