A white coating on the tongue is most often due to overgrowth of the fingerlike projections (called papillae) on the surface of the tongue known as hypertrophy of tongue papillae. Common causes of hypertrophy of tongue papillae include:
- Poor oral hygiene
- Dehydration
- Mouth breathing
- Poor dentition
- Smoking and alcohol abuse
The tongue can be cleaned with your toothbrush or with a tongue scraper. I will usually recommend doing it twice a day after you've brushed your teeth. It is not harmful to scrape your tongue more than twice a day, but like most things in life, too much of anything is probaly not good. To prevent a white tongue appearance, you should practise good oral hygiene, ensure adequate hydration and stop smoking. If you are a mouth breather due to a blocked nose, you should visit an ENT Specialist for an assessment.
There are other causes of white appearance on the tongue such as leukoplakia (white patch that cannot be scrapped off), candidiasis (fungal infection), lichen planus (due to a problem with your immune system) and syphilis (sexually transmitted disease).
If you are concerned, you should visit your doctor or dentist for an assessment.
Hope this helps and all the best!
