Explanation for Warming Sensation when Rubbing Oil Soap Mixture

The warming sensation you feel when rubbing the mixture of Oil Soap and natural oils is likely due to the interaction between the surfactant blend in the Oil Soap and the oil phase, combined with the physical friction generated during rubbing.

Oil Soap contains a blend of surfactants designed to mix with oils and water. When you rub this mixture, the surfactants are actively interacting with the oils. This physical process of dispersion or potential initial emulsification upon rubbing can sometimes release a small amount of energy, which might be perceived as a mild warming sensation on the skin. The act of rubbing itself also generates friction, contributing to the feeling of warmth.

The product description for Oil Soap does not indicate that mixing it with oils at room temperature causes a significant exothermic (heat-releasing) chemical reaction. Therefore, the warmth is more likely related to the physical dynamics of the mixture and the act of rubbing rather than a chemical reaction.

Using Oil Soap at 45% with natural oils is within the typical usage range (15-40% for normal-oily skin, though your formula is slightly higher, it's still a common concentration for oil-based cleansers) and is consistent with example formulations provided for the product.