For about 3-4 weeks now, I've had a dull taste in my mouth. I can't seem to shake it, but I don't have any other symptoms that I can tell. Food tastes fine. Some drinks (Diet Caff Free Mt. Dew, for example) don't taste as strong as they used to. Brushing my teeth and mouthwash don't make it go away. I drink rinse & gargle with hydrogen peroxide, and it went away temporarily but came back later in the day.
One thing: I drink at least 16 oz. of coffee each day. I've wondered if too much coffee is causing it. I've had stomach acid problems in the past, and I've wondered if that's causing it, but I'm just not noticing the acid. Usually, though, when I have acid problems, I taste acid, but this is just a dull flavor that's not particularly pleasant but not quite bad.