Why does this yellow coating on my tongue keep coming back?

It's plaque: Some people have more of it than others. Nothing abnormal. Just make sure you are brushing your tongue as well as part of your daily hygiene regimen. If its of concern get evaluated by your physician or dentist. Hope this helps.

Brush tongue: The coating is plaque, the same thing that builds up on your teeth. Brushing your to gue or using a tongue scraper will remove it. But must like the plaque on your teeth it will keep co inge back. It can be worse when you are sick, like with a cold or virus, or certain foods. Some people have more than other.Tongue cleaning will keep it under comtrol.

Bacterial playground: The mouth is a warm, dark, moist place full of bacteria that multiplies every 12 hours or so. Use a tongue scraper--best thing yet to help clean tongue--amazing (and kinda gross when you see it work!). Rinses are like washing your car with spray from a hose, when dry, it's still dirty- you gotta scrub to clean- teeth too! plaque grows almost everywhere in the mouth. Floss, brush & scrape 2 x daily.

Tongue catches all: The tongue is very much like a carpet. It catches and traps almost anything. So if what you eat and drink can color or stain your tongue. In order to remove the staining you can use a tongue scraper as the others described.