Castile soap is the world’s oldest and most celebrated natural soaps. Known for its purity, simplicity, and gentleness, this olive oil–based cleanser has stood the test of time across centuries and continents. But what exactly is Castile soap? How does it compare to other historic soaps like Aleppo Soap or Savon de Marseille? And how has it evolved in different countries?

At its core, Castile soap is a vegetable oil–based soap, traditionally made using 100% olive oil, water, and lye (sodium hydroxide) by being 'baked' in a cauldron. Unlike soaps that include animal fats (tallow), authentic Castile soap is entirely plant-based, biodegradable, and suitable for sensitive skin.

Key characteristics:

• Mild and moisturizing

• Free from synthetic detergents

• Ideal for skin, hair, and household cleaning

Modern versions sometimes blend olive oil with coconut, sunflower, or castor oils for better lather, but the core philosophy remains the same: gentle, clean, and green.

The story of Castile soap begins in Castille, — a region of Spain with rich olive groves and access to early soapmaking techniques brought from the Arab world.

Between the 12th and 14th centuries:

• Muslim and Jewish soapmakers fleeing persecution brought their knowledge to southern Europe.

• These artisans introduced olive oil–based soap production to Spain, particularly in Castile, where animal fats were scarce but olives were abundant.

Castile soap gained fame for being:

• Cleaner-burning (without lard/tallow)

• More suitable for delicate fabrics and skin

• Highly valued among European nobility

By the 16th century, Castile soap had become a pan-European export, often seen as a luxury item and precursor to many modern plant-based soaps.

Here’s how Castile soap compares to three other legendary Mediterranean soaps:

Oldest soap in the world, dating back over 2,000 years and the original inspiration for what has become known as Castille Soap .

• Base oils: Olive oil + laurel berry oil

• Method: Baked in a Cauldron for 14 days between December & March each year (immediately following the olive harvest); cut, stamped and cured for 9 months before being ready to use.

• Color: Green exterior with brown patina; earthy scent

• Skin benefits: Laurel oil adds antimicrobial properties; used for acne, eczema

Difference: While both use olive oil, Aleppo's unique formulation also uses laurel oil. This makes it green in colour when not exposed to the air, and particularly beneficial for troubled and difficult skin types and conditions.

Originated in the port city of Marseille, France, in the 17th century.

• Base oils: Olive oil (green soap) or palm/coconut oil (white soap)

• Tradition: Cooked for 10 days in cauldrons ("Marseillaise method")

• Format: Large cubes or blocks, often stamped

• Usage: Household cleaning, laundry, body care

Difference: Traditional Marseille soap can be formulated with Olive, Palm and Coconut Oils. Castile soap is traditionally 100% olive oil, Aleppo Soap exclusively uses Olive Oil & Laurel Oil. 

Over time, other nations adopted and adapted the Castile term:

• Italy: Especially in Liguria and Naples, olive-based soaps were infused with herbs or citrus.

• Portugal: Known for minimalist, high-quality Castile-style soaps still handmade today.

• Modern USA: The 'Castille' term has been adopted by Dr Bonner's who make non traditional "Liquid Castile soap". Blends such as olive with coconut and hemp oils and the addition of fragrance and other non-authentic ingredients. We don't consider this proper Castille soap, which should be fragrance & allergen free, multipurpose and gentle.

Castile soap is more than just a cleanser — it's a symbol of sustainability, tradition, and minimalism. In a world full of synthetic surfactants and chemical cleansers, Castile soap remains:

• Zero waste (especially in bar form)

• 100% Plant Oil (traditionally)

• Safe for sensitive skin and babies

• Versatile (can be used as body wash, shampoo, dish soap, pet wash, and more)

Castile soap is a phrase that is regularly used to describe hypoallergenic, fragrance free solid soaps made predominantly with olive oil, within the Mediteraniaen region. 

It does not have protected status for a particularly Spanish region, and is now a category and methodology that encompasses authentic and original Spanish, Syrian & Marseille soaps. All of these, when properly made, are the most pure, adaptable, and time-honored soaps in the world.

Castille-Type soaps is a phrase used around the world. These soaps are manufactured and adapted to include fragrance and liquids formats. Whilst they are made with plant oils, they are not true Castille soaps. 

Proper Castille Soap is very relevant today: the simple eco friendly, multipurpose formulas, are economical and environmentally friendly in process, ingredients and sustainability.  Few skincare products can claim a legacy like Castile soap — and fewer still can do so with just three simple ingredients.

At French Soaps we import Traditionally made, authentic Aleppo Soap made in the centre of Aleppo City in Syria. 
We stock Traditional & Authentically made Marseille soap made by two of the original Savonneries in Marseille. 

We do not stock copies, adaptions or product from any savonnerie we have't visited and verified. 

Our extensive range of proper Aleppo Soaps here.