They look similar from across a market stall. Both are solid bars. Both are natural. Both have olive oil as their base. Both have been around for centuries. The person selling them will sometimes use the names interchangeably.
They are not the same thing.
What they share
Castile soap — named for the Castile region of Spain — is traditionally made from 100% olive oil. Saponified with sodium hydroxide, it produces a hard, ivory-white bar that is gentle, moisturising, and free of the synthetic additives common to commercial soap.
Aleppo soap shares the olive oil base but adds laurel berry oil — the pressed oil from the fruit of Laurus nobilis. The proportion of laurel oil in an Aleppo bar ranges from a few percent up to seventy-five percent or more, depending on the intended use.
Both soaps are ancient. Castile soap was being produced in Spain by the 12th century, partly inspired by the Levantine soap tradition that Aleppo already represented. Both are natural, minimal-ingredient formulations. Both are appropriate for sensitive skin at low concentrations.
The critical difference
Olive oil, the Castile base, is a moisturiser and cleanser. It provides oleic acid that nourishes the skin barrier, retained glycerin that humectifies, and gentle surfactancy from saponification. What it does not provide is antibacterial, antifungal, or anti-inflammatory activity. Pure olive oil soap is a passive product — it cleanses and nourishes without actively treating any skin condition.
Laurel oil, the addition in Aleppo soap, changes this entirely. Lauric acid is bactericidal. Linalool is antifungal and anti-inflammatory. 1,8-cineole is antimicrobial. Beta-pinene is antiseptic. These are active compounds with measurable effects on skin conditions. They are not present in Castile soap.
This is the difference between a nutritious meal and a nutritious meal with therapeutic supplements. The Castile base is the meal. The laurel oil is where the treatment begins.
When Castile wins
For pure moisturisation and barrier support with no active ingredient need — ultra-dry skin, newborn washing, elderly skin, post-procedure care, maximum gentleness — Castile-style soap is the right choice.
Avlia makes its own Castile equivalent: the Avlia 100% Olive Oil Bar (0% laurel). The same hand-pour, hand-stamp process by Syrian Sabonji artisans; the same olive oil quality; no laurel oil at all. If you want a Castile soap made by artisans whose tradition predates Castile soap's existence, Avlia's 0% bar is it.
When Aleppo wins
Acne: Castile soap has no antibacterial activity against acne-causing bacteria. Aleppo soap's lauric acid does. Advantage: Aleppo.
Dandruff: Castile soap has no antifungal activity against Malassezia. Aleppo's laurel oil terpenes do. Advantage: Aleppo.
Eczema: both are gentle; Aleppo's anti-inflammatory compounds add measurable benefit. Advantage: Aleppo.
Body odour: Castile soap cleanses; Aleppo soap also reduces the bacterial population that causes odour. Advantage: Aleppo.
Scalp health: Castile soap is a neutral shampoo; Aleppo with high laurel content actively treats scalp conditions. Advantage: Aleppo.
For conditions where the skin is healthy and the goal is simply clean, well-moisturised skin, the two soaps are comparable. The Avlia 5% Bar, for instance, is so close to a Castile soap in composition that the difference is nearly academic for daily use.
The Avlia advantage: both in one brand
Avlia's range spans 0% laurel (pure Castile equivalent) to 75% laurel (maximum Aleppo potency) in a single product line. You can start at 0% and move toward the percentage that works for your conditions — using the same brand, the same trusted Syrian Sabonji artisan production from Turkey, throughout.
Find the full range at avliahome.com.