In some healthy people, furry tongue appears to be a normal condition of unknown cause. Because it can be something of a hygiene problem, I recommend regular tongue brushing and scraping (with a downward-bent, commercially available scraper). Scrape as far back as possible. You’ll gag at first, but this reflex is quickly overcome. Gargling with bicarbonate of soda — as already suggested — helps hygiene. Or use dilute (1%) hydrogen peroxide (but peroxide may aggravate the condition in some people). None of this cures the problem, but it does control the condition with little effort.