Soap nuts contain saponin, a natural detergent. The soap nut shell absorbs water and releases the saponins which circulate as a natural surfactant in the wash water, freeing dirt, grime, and oils from clothing. I thought so too, but was amazed that they actually work.Soap nuts contain saponin, a natural detergent. The soap nut shell absorbs water and releases the saponins which circulate as a natural surfactant in the wash water, freeing dirt, grime, and oils from clothing. I thought so too, but was amazed that they actually work.