The coating may be quite commonly seen in healthy adults, more often in those who have missing teeth, those on a soft diet, those with poor oral hygiene and those who are fasting. People who are fasting may be drinking an inadequate amount of fluid to replace what is lost through respiration, sweating and urination.

Not drinking enough water

Someone on a soft diet may also not be drinking enough water, either due to habit or lack of thirst stimulation for various reasons. A soft diet does not necessarily mean that there is a greater intake of fluid. The amount of water required depends on the amount that is lost and the salt intake. The higher the salt consumption, the more water one needs. The spaces left by missing teeth may tend to accumulate food debris.

Poor oral hygiene

Sub-optimal oral hygiene could lead to a person having a white coating that could otherwise have been removed. The tongue can become coated with off-white debris in people with various illnesses, especially those with poor oral hygiene or those who are dehydrated. The coating can usually be scraped off at least partially.

Weak immune system

In a small number of patients who have weakened immune systems, a white layer on the tongue may be a fungal infestation, which can be rubbed off, leaving a bleeding surface. The fungal infestation can be treated with anti-fungal medication. Perhaps the most sensible advice is to ensure sufficient intake of water and, if the furred tongue still persists over time, a visit to the dentist should be helpful in clearing up any doubts.​​​

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Ref: S13