Olive oil soap, also commonly known as castile soap, is beneficial to the skin because of the olive oil it contains. Olive oil has been used for centuries for topical skin treatments (and as salad dressing). Olive oil helps to prevent skin damage, smooth fine lines and wrinkles, provide moisture and protect the skin from damage by the environment.

Oxidation occurs when oxygen comes into contact with our skin, which has toxins (free radicals) on it. Those are bonded with our electrons and they bond with the oxygen; this oxidation steals electrons from our skin and causes damage to our skin cells. Ultimately, oxidation results in wrinkles, as one atom after another loses electrons and tries to bond with an electron next to it (which belongs to another atom). All these atoms pull in tighter than they should, causing a "fissure" or what we know as a wrinkle. Olive oil is an antioxidant, meaning that it interferes with the process of oxygen bonding to those free radicals. It may slow or even completely prevent oxidation for certain cells, meaning that whole cells are not damaged by oxidation. Undamaged cells will help maintain a smooth, unwrinkled skin surface.

The fat composition of olive oil is very similar to that of human skin. This means that olive oil rarely causes any kind of allergic reaction. It is quickly and easily absorbed by the skin, so it doesn't leave a greasy feeling or simply a top coat of oil that will rub off on the next thing you touch. It helps the skin to absorb and keep moisture, which prevents chapping, flakiness and irritated red areas from forming on the skin.

Olive oil contains high levels of Vitamin E, which is very beneficial for skin. Vitamin E also is an active antioxidant, helping to protect our skin cells from the environmental factors that produce free radicals. Additionally, vitamin E regulates the levels of vitamin A in the body, helps smooth out already damaged skin (such as wrinkles and scar tissue), protects the skin from UV light damage, reduces water loss from the skin and provides a barrier between the skin and harmful environmental factors.