Soap locust can have the decontamination effect of soap. Saponin contains saponin, which has surfactant-like properties: foaming, decontamination, and emulsification. It is more resistant to hard water than real soap, does not contain alkaline, and does not damage silk and wool fabrics.
There are many kinds of soap locust, with different descaling abilities. "Newly Revised Materia Medica" in the early Tang Dynasty records: "The pig tooth acacia is the lowest, with a curvy and thin shape, no moisture at all, and cannot be washed away." The one with "thin skin, fleshy flesh... strong flavor" should be selected, so it is known in later generations. The word "soap" or "soap locust" is used to refer to the high-quality and thick-fleshed soap locust, which means "thick and fleshy soap locust". Li Shizhen's "Compendium of Materia Medica" of the Ming Dynasty said: "Soap pods...pick the pods in October, boil and mash them, mix them with white flour and various fragrances to make pills, bathe the body and face to remove dirt, and the greasy and moisturizing effect is better than that of soap pods." It can be seen from this that soap locust really has a decontamination effect.