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Castile soap is a natural liquid or hard soap made from vegetable oils. The first Castile soaps were made with the local olive oil and contained no tallow, or rendered animal fats, like most contemporary soaps. Today, Castile soap appears in many stores, often scented with essential oils, as a multipurpose cleanser.

Natural Vegetable Ingredients

Castile soap contains only vegetable-based ingredients, often produced organically and sourced using fair trade principles. One brand of Castile soap in the United States uses a blend of coconut, olive, hemp and jojoba oils plus water and essential oils for fragrance.

Minimal Environmental Impact

According to the authors of "The Urban Homestead: Your Guide to Self-Sufficient Living in the Heart of the City," Castile soap does not contain synthetic fragrances or detergents that can upset the balance of the environment when it enters the wastewater stream. Because the formula is nontoxic, most people don't need to wear rubber gloves or worry about skin irritation while cleaning with Castile soap. In addition, the soap may also be packaged in post-consumer recycled plastic bottles.

Clean Lathering

Castile soap provides a clean, fluffy lather in both hard and soft water. Potassium hydroxide converts the oils into soap and glycerine, thus requiring less water for a lather than traditional liquid soap. "Real Simple" magazine suggests using diluted Castile soap to wash your car's exterior, windshield and hubcaps: the gentle, non-abrasive solution won't leave streaks.

Multipurpose Formula

Though it's most commonly used as a body wash, shampoo and even toothpaste, Castile soap tackles nearly every cleaning task in the home. "The Urban Homestead" suggests adding a tablespoon of Castile soap to a quart of water for an all-natural, all-purpose cleanser. The soap cuts through grime in kitchens, bathrooms and other hard surfaces. A quarter-cup added to laundry cleans clothes without harsh detergents.

Long-Lasting Liquid

Castile soap is often sold in concentrated form, making it an economical option for frugal users. Consumers should dilute the liquid before use according to the package directions.