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Castile Soap: What It Is, How It's Used in Green Cleaning & More!


Different Brands of Eco-Friendly Liquid Castile Soaps

Different Brands of Eco-Friendly Liquid Castile Soaps

Photo © Karen Peltier

Definition: So what is castile soap exactly? Castile soap is a vegetable soap traditionally made from 100% pure olive oil, water, and lye. Therefore, it is a vegan product because it does not include the addition of animal fats as some other soaps might. It is believed to have originated from a region in Spain historically called Castile - hence the name castile soap.


Sometimes castile soap is called olive oil soap.


Several modern formulations have tweaked the time-honored original recipe with the addition of natural ingredients, such as:

  • aloe vera gel (for moisturizing benefits)
  • "butters" (e.g., shea butter)
  • essential oils (e.g., peppermint, lavender)
  • natural antioxidants and preservatives (e.g., rosemary extract, citric acid, Vitamin E)
  • salt (used in bar soaps to make them harder and last longer)
  • vegetable oils (e.g., hemp, coconut, avocado oils, etc.)

True castile soap does not contain harsh synthetic detergents and the best ones don't add any skin-irritating artificial colorants, fragrances, or preservatives.

Types Available

Castile soap is available in bar or liquid form. For some great brands to choose from, check out "Top Castile Soaps for Green Cleaning."

Green Cleaning Uses

Did you know that you can use castile soap to clean your house inside and out?

Castile soap is indispensable in green cleaning because it acts as a surfactant and helps lift away dirt and cut through grease. Discover all the ways you can clean with it inside your home, including as a laundry detergent and a dish soap, in the article "Use Castile Soap to Clean Your Whole House From Top to Bottom!"

Because it's eco-friendly and biodegradable, it's also great for cleaning outside your home. So, if you need to wash your car or clean your patio furniture, reach for the liquid castile soap!

Want to try making your own homemade eco-friendly cleaners with castile soap? Check out these fantastic green recipes that are easy, fast, and cost-effective:

Other Uses

Castile soap has many personal care uses, such as using it as a shampoo, shaving cream, body wash, and even a toothpaste! (Try peppermint if you're brave enough to brush your teeth with it!) Also, it's great for washing your pets!


Castile soap is often very reasonably priced and for green cleaning uses, the liquid soap is a great deal! Many manufacturers offer a variety of sizes, including gallons, so buy large and save big time!

Shelf Life

How long does castile soap last exactly? This is the question I asked a leading castile soap manufacturer. The company representative indicated that a three-year expiration date is typical for both its bar and liquid soaps; however, she noted that you can often use it beyond the expiration date, but that the essential oils would be diminished. When in doubt, contact the manufacturer. The lot code will often help determine the product expiration date.

In addition to the expiration date, another thing to keep in mind would be how you store your soap. For example, if liquid soaps are not closed well and kept in a shower for example, then the possibility of contaminants entering the product increases. So this means the formulation may be compromised, especially if it doesn't contain any preservatives.

Safety & Environmental Notes

All-natural castile soap is a green product because it is biodegradable, non-toxic, and safe to use for cleaning and personal care uses.


Because it's soap, it's regulated by the Consumer Product Safety Commission (CPSC), not by the FDA.

The term "castile soap" doesn't appear to be regulated in any way, so look out for companies adding in synthetic detergents and using hardly any olive oil at all!

Soap Making Process

To make liquid castile soap, three main ingredients − water, olive oil, and potassium hydroxide − are used.

To make bar soap, sodium hydroxide is used to saponify the oils. For more information, check out the articles "Olive Oil (Castile) Recipes" and "How to Make Soap from Scratch - Soap Making Using the Cold Process Method" by David Fisher, About.com Candle and Soap Making Guide.


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