Cincinnati (AP) -- Persistent consumer complaints are causing some stains on a Procter & Gamble Co. Crest product's reputation.

Crest Pro-Health Rinse hit the market three years ago as an alcohol-free mouthwash that not only freshens breath but fights oral maladies such as gingivitis and plaque.

The strong-selling product has caused some users to report discoloration of their teeth and numbing taste.

P&G says "99.99 percent" of users have had no complaints and that any discoloration or aftertaste is temporary.

But NBC's "Today" show reported Wednesday that the complaints have led to a consumer lawsuit and further study by the Food and Drug Administration, which approved the product as safe and effective.

(Copyright 2008 by The Associated Press. All rights reserved.)