Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Why, oh why do you keep changing the formula, Dr. Ken?

Both my wife and I kept getting stained teeth from alcohol-based mouthwashes, so about three years ago, much research and experimentation led us to become fans of Dr. Ken's amazing, all-natural, alcohol-free mouthwash. My wife is very particular about the taste of her mouthwash, which had already ruled out Biotene.In the intervening years, it seems Dr. Ken keeps diddling with the formula. The first twist was not bad, as it "lighened" the wash somewhat (you will note that this mouthwash will stain your porcelain sinks, unless you diligently rinse and wipe the sink each time after rinsing).But the last batch we bought from Amazon has not only new packaging (a white bottle), but has a completely different balance of ingredients, and it tastes TERRIBLE! I don't mind as much, but my wife can no longer stand the stuff, so it's back to the drawing board to find a new mouthwash.Wish I knew why you had to spoil a good thing, Dr. Ken.