# What Is Castile Soap? How It Differs From Marseille and Aleppo

> <p>Castile soap is a plant-oil soap named for Spain's Castile region. Sources disagree on whether it must be olive-only; this guide covers what it is made of, what it is used for, and how it differs from Marseille and Aleppo soap.</p>

- **URL:** https://sampsonecoshop.com/blogs/sampson-learning-center/what-is-castile-soap-and-how-it-differs-from-marseille-and-aleppo

Castile soap is a true soap made by combining plant oils with an alkali, named for the Castile region of Spain. This guide covers what it is, what it is made of, what it is used for, and how it differs from Marseille and Aleppo soap.

We do not currently list a castile soap, but we sell two soaps from the same family: [traditional Aleppo soap](/products/traditional-aleppo-soap), which Wikipedia describes as castile's ancestor, and [Authentic Marseille Soap](/products/authentic-marseille-soap). Read this with that in mind. Where sources disagree, we say so. For head-to-head comparisons, see our [Marseille vs castile](/blogs/sampson-learning-center/marseille-soap-vs-castile-soap-which-should-you-actually-use) and [Aleppo vs castile](/blogs/sampson-learning-center/aleppo-soap-vs-castile-soap) guides.

In this guide [What Is Castile Soap?](#what-is-castile-soap) [Is Castile Soap Only Made From Olive Oil?](#is-castile-soap-only-made-from-olive-oil) [Where Does Castile Soap Come From?](#where-does-castile-soap-come-from) [What Is Castile Soap Used For?](#what-is-castile-soap-used-for) [How Is Castile Soap Different From Marseille and Aleppo Soap?](#how-is-castile-soap-different-from-marseille-and-aleppo-soap) [Does Castile Soap Have Downsides?](#does-castile-soap-have-downsides) [How Do You Choose a Castile Soap?](#how-do-you-choose-a-castile-soap) [Does Sampson Sell Castile Soap?](#does-sampson-sell-castile-soap) [Frequently Asked Questions](#faq)

 **Key takeaways**

Castile soap is a true soap made by reacting plant oils with an alkali. Traditionally that meant olive oil from Spain's Castile region; today brands also use coconut, hemp, jojoba and other oils.

Sources disagree on the definition: Wikipedia calls castile an olive oil-based soap, while Dr. Bronner's and the David Suzuki Foundation describe plant-oil blends. We found no single standard, so the ingredient list is your guide.

Per Wikipedia, castile descends from Aleppo soap once the laurel oil was dropped. Our Aleppo bar keeps the laurel; our Marseille bar is palm-based by its listing, so neither is an olive-only castile.

Castile soap is alkaline, roughly like baking soda according to Dr. Bronner's, and diluted mixtures are no longer self-preserving. Mix small batches and replace them within weeks.

## What Is Castile Soap?

Castile soap is a hard or liquid soap made from plant oils and an alkali. [Wikipedia](https://en.wikipedia.org/wiki/Castile_soap) defines it as an olive oil-based soap made in the style that originated in the Castile region of Spain.
- **The broad definition:** [Dr. Bronner's](https://www.drbronner.com/pages/what-is-castile-soap) describes castile soap as made from vegetable oils with no animal fats, sold in liquid and bar form.
- **A true soap:** Dr. Bronner's says castile is a true soap, made by saponifying plant oils with an alkali such as potassium hydroxide or sodium hydroxide, rather than a synthetic detergent.
- **The name:** Wikipedia says it is called castile because it was produced on a large scale in the territories of the Crown of Castile and exported across Europe.

## Is Castile Soap Only Made From Olive Oil?

Traditionally yes, but today it depends on the brand. Sources disagree, and we found no single standard that defines the name, so the ingredient list is the only reliable guide.
- **The strict view:** Wikipedia defines castile as an olive oil-based soap.
- **The modern view:** Dr. Bronner's says castile can be made from a variety of plant oils and lists its own blend as coconut, palm, olive, hemp and jojoba oils. The [David Suzuki Foundation](https://davidsuzuki.org/living-green/how-to-use-castile-soap/) lists coconut, hemp, sunflower seed, jojoba and olive.
- **Palm oil:** The David Suzuki Foundation advises avoiding brands that use palm oil because of its effect on biodiverse forests, yet Dr. Bronner's lists palm oil in its blend. The two sources diverge.
- **The alkali:** The David Suzuki Foundation says sodium hydroxide makes solid soap and potassium hydroxide makes liquid soap.
- **The label trap:** The same source warns that liquid soap does not mean plant-based, so read the label.

## Where Does Castile Soap Come From?

Castile soap descends from Aleppo soap. [Wikipedia](https://en.wikipedia.org/wiki/Castile_soap) says Aleppo soapmakers in the Levant made hard soaps from olive and laurel oil for millennia, and Mediterranean soapmakers later dropped the laurel, leaving an olive oil soap.
- **The route west:** Wikipedia says it is commonly believed that the Crusaders brought Aleppo soap to Europe in the 11th century, after which production spread around the Mediterranean. It presents this as a common belief, not a settled fact.
- **The white bar:** Wikipedia says adding brine made the soap float for skimming, which probably produced the first white hard soap, jabón de Castilla, while Aleppo soap tends to be green.
- **The name in print:** Wikipedia cites London port records of Castile soap imports from 1567 to 1568 and a mention in an English poem dated 1436 or 1437.

## What Is Castile Soap Used For?

Brands market castile soap as a multi-purpose cleaner for body and home. We found no trial testing those uses, so treat the lists below as what the makers say, not as proven results.
- **Body:** Dr. Bronner's lists washing hair, face, body and hands, plus shaving and makeup removal.
- **Home:** Dr. Bronner's lists dishes, laundry, mopping and all-purpose spray. The David Suzuki Foundation adds washing fruit and vegetables with a squirt in a sinkful of water, floors and the car.
- **Pets:** Dr. Bronner's says diluted soap can wash dogs, that you should avoid the eyes and ears, and that cats can be sensitive to essential oils, so unscented is the choice for them. Ask a veterinarian first.
- **Hair:** Dr. Bronner's says true soap is alkaline, so follow it with an acidic rinse and allow time to adjust.

Featured in this guide

Traditional Aleppo Soap

Olive oil, laurel berry oil, water and lye, air-cured for at least nine months, in four laurel strengths. Full details are on the product page. [Shop now →](/products/traditional-aleppo-soap) ✓ 30-day money-back guarantee · Free shipping over $75

## How Is Castile Soap Different From Marseille and Aleppo Soap?

All three are traditional plant-oil soaps and they differ mainly in the oils. Castile is olive-based by the older definition, Aleppo adds laurel berry oil, and Marseille is defined by trade-group rules rather than one oil.
- **Castile vs Aleppo:** Per Wikipedia, castile is essentially Aleppo soap without the laurel. Our [traditional Aleppo soap](/products/traditional-aleppo-soap) lists four ingredients, olive oil, laurel berry oil, water and lye, with laurel at 1%, 5%, 25% or 40% depending on the bar. See our [Aleppo soap guide](/blogs/sampson-learning-center/what-is-aleppo-soap).
- **Marseille:** The UPSM trade group's charter for traditional Marseille soap requires at least 72% vegetable oil and no perfume, colorant or additive, as we cover in our [Marseille vs castile guide](/blogs/sampson-learning-center/marseille-soap-vs-castile-soap-which-should-you-actually-use). The name itself is not a protected geographical indication. See our [Marseille soap guide](/blogs/sampson-learning-center/what-is-marseille-soap).
- **Our Marseille bar:** Our [Authentic Marseille Soap](/products/authentic-marseille-soap) is, per its listing, a scented bar built on saponified palm and palm-kernel oils with shea butter and glycerin, made by Savonnerie Alpilles in Provence. It falls outside both the olive-only definition and the palm-free advice above.

## Does Castile Soap Have Downsides?

A few practical ones. Castile soap is alkaline, diluted mixtures spoil faster than the concentrate, and results vary by hair and skin. This is general information, not medical advice.
- **Alkaline:** [Dr. Bronner's](https://www.drbronner.com/pages/what-is-castile-soap) says castile soap tends to be alkaline, about the level of baking soda and well below bleach.
- **Hair:** Dr. Bronner's says results depend on hair type and water conditions.
- **Dilution:** Dr. Bronner's says diluted castile soap is no longer self-preserving. Make only what you will use within a couple of weeks and replace any remainder after about one month.
- **Scents and pets:** Dr. Bronner's advises avoiding its Tea Tree scent on dogs and choosing the unscented version for cats.
- **Evidence:** We found no clinical trial comparing castile soap with other cleansers on skin or hair.
- **When to ask a professional:** If you have eczema, dermatitis or a persistent rash, ask a dermatologist before changing cleansers, and stop if skin turns itchy, raw or inflamed.

## How Do You Choose a Castile Soap?

Read the ingredient list, because the name does not guarantee what is inside. Check the oils, the alkali and whether it is scented, then match the form to the job.
- **The oils:** Decide between olive-only, as Wikipedia defines it, and a blend. The David Suzuki Foundation names coconut, hemp, sunflower seed, jojoba and olive as typical plant oils.
- **Palm oil:** If palm matters to you, look for it on the label, since the sources above disagree.
- **Scent:** The David Suzuki Foundation lists scent-free as a feature of authentic castile. Dr. Bronner's notes that essential-oil scents matter for pets.
- **Form:** Dr. Bronner's says liquid is easy to measure and dilute for cleaning, while bar soap is compact but may need grating or dissolving first for household recipes.

## Does Sampson Sell Castile Soap?

Not at the moment. We do not currently list a castile soap, so we will not claim our bars are one. The closest we stock is traditional Aleppo soap, which keeps the laurel oil that castile dropped.

We sell our Aleppo and Marseille bars as body soaps and make no claim about household cleaning. If you want liquid castile for diluted cleaning recipes, check the oils and scent on the label first.

## Frequently Asked Questions

What is castile soap?

Castile soap is a true soap made by reacting plant oils with an alkali, named for Spain's Castile region. Wikipedia defines it as olive oil-based; modern brands often use blends of plant oils.

Is castile soap vegan?

Castile soap made only from vegetable oils contains no animal fats, and both Dr. Bronner's and the David Suzuki Foundation describe it as vegan. Check the label, since not every liquid soap is plant-based.

Does castile soap expire?

Dr. Bronner's says its liquid has a recommended shelf life of three years from manufacture, used within 24 months once opened. Diluted mixtures last far less, about a month at most.

Is castile soap the same as Marseille soap?

No. Castile is olive-based by the older definition, while Marseille is defined by trade-group rules such as at least 72% vegetable oil. Marseille bars can use other oils, including palm.

Can you wash your face and hair with castile soap?

Dr. Bronner's lists face and hair washing among its uses and says hair needs an acidic rinse afterwards. We found no trials, so patch-test first and stop if skin becomes irritated. [See Traditional Aleppo Soap — 30-Day Guarantee](/products/traditional-aleppo-soap)

## Related Articles [Marseille Soap vs Castile Soap: Which Should You Actually Use? →](/blogs/sampson-learning-center/marseille-soap-vs-castile-soap-which-should-you-actually-use) [Aleppo Soap vs Castile Soap: Which Should You Use? →](/blogs/sampson-learning-center/aleppo-soap-vs-castile-soap) [African Black Soap vs Castile Soap: Which Is Better for Your Skin? →](/blogs/sampson-learning-center/african-black-soap-vs-castile-soap) [What Is Aleppo Soap? The World's Oldest Soap Explained →](/blogs/sampson-learning-center/what-is-aleppo-soap) [What Is Marseille Soap? The French Soap That's Stood the Test of Time →](/blogs/sampson-learning-center/what-is-marseille-soap) [When Was Soap Invented? Earliest Evidence and Where Aleppo and Marseille Fit →](/blogs/sampson-learning-center/when-was-soap-invented-and-where-aleppo-and-marseille-fit)