We appreciate you sharing this with us and understand how upsetting this must be, Russell. Please know certain versions of Crest Pro-Health Rinse contain cetylpyridinium chloride (CPC), an ingredient that not only helps to fight plaque and gingivitis but also kills bacteria in the mouth. For a small percentage of people who use the product, after it kills germs in your mouth, those dead germs can collect on the tooth surface and create the appearance of stains. Rest assured the discoloration is reversible and largely preventable. To help remove and prevent the discoloration, we recommend using a tartar-control or whitening toothpaste, a power toothbrush, and floss. Your feedback is truly important to us and will be shared with our team. We'd be happy to help you find a mouthwash that meets your oral care needs. Please call us at (800) 566-7252 so we can assist you further.