Dr. Elsey is passionate about providing the very best products for your cats. Over the past year, it became impossible to guarantee that the previous Respiratory Relief clay formula would meet our high standards and the dust content became inconsistent. We have recently switched to a different clay mixture in an effort to keep Respiratory Relief as low dust as possible. The new clay is slightly darker than the clay we were using because it is mined in a different area. The color will not interfere with performance.