Table of Contents
Updated November 2026
Castile soap is a simple, plant-based soap made by turning vegetable oils like olive and coconut into soap. The main benefits of castile soap are that it's biodegradable, free of synthetic detergents and fragrance, and versatile enough to clean your hands, body, dishes, floors, and counters with one bottle. It's also a helpful partner for essential oils in aromatherapy, because it carries them through bath water. Below I explain what it's made from, why it cleans so well, how brands differ, and the ways I use it around the house. Jump to the ways to use it
This post is all about castile soap itself. To scent it, see my best essential oils to mix with castile soap and my castile soap recipes.
This post contains affiliate links. If you buy through them, I may earn a small commission at no extra cost to you.
What Is Castile Soap?
Castile soap gets its name from the Castile region of Spain, where soap makers first became known for making it from olive oil. Today the name is used for most soaps made only from plant oils, with no animal fats or synthetic detergents. You'll find it as a bar or as a concentrated liquid.
What Castile Soap Is Made From
All true soap is made through a process called saponification. Oils are mixed with an alkali, and the two react to become soap and glycerin. Liquid castile soap is made with potassium hydroxide, and bar soap is made with sodium hydroxide. When the soap is made correctly, none of the alkali is left in the finished product.
On the label, you'll often see the soap listed by the oils it came from, like "saponified coconut and olive oils," or by names like potassium olivate (from olive oil) and potassium cocoate (from coconut oil). Common oils include:
- Olive oil: the original choice. Mild and gentle, with a softer lather.
- Coconut oil: adds big, bubbly lather and strong cleaning power, but can feel more drying.
- Hemp, jojoba, and avocado oils: often added for a softer, more conditioning feel.
- Castor oil: helps create a rich, stable lather.
How Castile Soap Brands Differ
Not every bottle of castile soap is the same. When you compare brands, look at:
| What varies | Why it matters |
| Oil blend | Olive-heavy soaps are milder. Coconut-heavy soaps lather and clean more strongly but can feel more drying. |
| Concentration | Some liquids are thicker and more concentrated than others, so dilution amounts on the label can differ. |
| Scented or unscented | Scented versions already contain essential oils or fragrance. Choose unscented if you want to add your own oils or have sensitive skin. |
| Added ingredients | Many add glycerin, vitamin E or citric acid. These are common, but read the list if you have allergies. |
| Labeling | "Castile" isn't a regulated term. If the label lists synthetic detergents like sodium lauryl sulfate, it isn't true castile soap. |
I keep a bottle of unscented liquid castile soap (affiliate link) on hand. Whatever brand you choose, check that the ingredients are plant oils turned into soap, and that nothing in it bothers your skin.
Why Castile Soap Is a Good Natural Cleaner
Soap works because each soap molecule has two ends. One end is attracted to water, and the other grabs onto oil and grease. When you scrub, the soap surrounds greasy dirt and lifts it off the surface so water can rinse it away. That's why such a simple soap does so much.
Castile soap benefits at a glance
- Lifts grease, grime and everyday dirt
- Made from plant oils, with no synthetic detergents
- Biodegradable
- Unscented versions are free of added fragrance
- Concentrated, so one bottle goes a long way
- One soap for hands, body, dishes and household cleaning
What Castile Soap Can't Do
Castile soap is wonderful, but it isn't perfect for every job:
- It's alkaline, not pH neutral. That helps it clean, but it can feel drying on some skin and hair.
- It reacts with hard water. Minerals in hard water combine with soap and leave a dull film or soap scum, especially on glass and shower doors.
- It doesn't mix with acids. Vinegar or lemon juice breaks castile soap down into a greasy, curdled mess. Use them separately.
- It isn't a disinfectant. Soap removes dirt and germs from surfaces, but when you need to sanitize, use a registered disinfectant and follow the label.
- It stings your eyes. Keep it away from your eyes, and rinse with plenty of water if it gets in.
Ways to Use Castile Soap Around the House
You don't need essential oils to use castile soap. Here are the ways I use it plain. Every brand's concentration is a little different, so check your bottle's label for its own dilution guide.
| Use | How I use it |
| Hand washing | A small squirt on wet hands, or mix 1 part soap with 2 parts water in a foaming pump. |
| Body wash | A few drops on a wet washcloth or pouf. A little goes a long way. |
| Hand-washing dishes | Mix 1 part soap with 10 parts water in a squeeze bottle, or add a small squirt to a sink of water. Not for the dishwasher, since it makes too many suds. |
| All-purpose spray | 1/4 cup soap in 1 quart of warm water for counters, tables, sinks and appliances. |
| Floors | A small amount in a bucket of warm water. If floors look dull, follow with a plain water mop. |
| Laundry stains | Rub a drop into a fresh stain before washing. |
| Makeup brushes | Swirl brushes in warm water with a drop of soap, rinse well and lay flat to dry. See my makeup brush cleaner. |
| Houseplant spray | Many gardeners use 1 tablespoon in 1 quart of water as a leaf wash. Test on one leaf first, since some plants are sensitive. |
One use I don't recommend is washing fruits and vegetables with soap. Produce can absorb soap residue. A good rinse under cool running water, with a scrub brush for firm produce, is the better choice.
Should You Use Castile Soap as Shampoo?
Some people love it, and some don't. Because castile soap is alkaline, it can leave hair feeling rough or dull, especially in hard water. If you want to try it, dilute it with water, rinse well, and follow with a separate diluted apple cider vinegar rinse to help smooth your hair. Never mix the vinegar into the soap.
Castile Soap in Aromatherapy
Castile soap does a quiet but important job in aromatherapy. Essential oils don't mix with water. Drop them straight into a bath or foot soak and they float on top, where they can land undiluted on your skin. Stirring the oils into a little castile soap first helps carry them through the water, so the scent spreads evenly and your skin stays comfortable. Salt, milk, or carrier oil on their own don't do this.
- Bath and foot soaks: mix the essential oils into the castile soap in a small cup, then add it to the water.
- With Epsom salt: castile soap and Epsom salt react when premixed (the magnesium binds the soap, like hard-water scum). Pour the soap and oil mix into the water first, then add the salt.
- Hand soap and body wash: unscented castile soap lets the essential oils set the mood, from calming lavender in the evening to bright sweet orange in the morning.
- Keep it acid-free: vinegar and lemon juice break the soap down, so they stay out of your castile blends.
To choose your oils and see how many drops to add, read my 10 best essential oils to mix with castile soap. For step-by-step hand soap, body wash, bath, and cleaner recipes, see my castile soap recipes with essential oils.
A Few Safety Basics
• Keep castile soap out of your eyes, and rinse with plenty of water if it gets in.
• If your skin feels dry, use less soap or add a moisturizer afterward, and patch test a new brand or blend if you have sensitive skin.
• Keep essential oils away from babies under 2. With a baby in the house, use unscented soap for them.
• If you're pregnant, check with your doctor or midwife before adding essential oils to soap or a bath.
• Store soap and oils where pets and little hands can't reach. Soap shouldn't be swallowed, and neither should essential oils. If someone swallows an oil, call Poison Control at 1-800-222-1222.
• Never put oils on pets, and diffuse with a door open so they can leave. Cats are especially sensitive, including to tea tree, citrus, peppermint, eucalyptus, pine, wintergreen, cinnamon, clove, and ylang ylang.
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More Natural Cleaning Posts
- 10 Best Essential Oils to Mix with Castile Soap
- Castile Soap Recipes with Essential Oils
- 20 Essential Oil Cleaning Recipes
- Top 5 Essential Oils for Cleaning Naturally
- DIY Foaming Hand Soap
- Natural Foaming Body Wash Recipes
Ready to make your own soaps and cleaners? My Aromatherapy Supply Kits have the bottles and supplies you need, and my free essential oil guides are full of recipe ideas.
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