- A thin white coating can indicate a fairly recent "cold" or "deficiency" condition such as a common cold
- A thick white coating suggests food retention and sluggish digestion
- A sticky white coating indicates excess phlegm
- A thick yellow coating can be a sign of digestive problems such as constipation. If the coating is dry, the problem is usually with the stomach and intestines; if it is wet you may have excess phlegm.
- A thin yellow coating can signify a lung infection
- A greyish or black tongue coating (yes, the coating can actually be black!) usually indicates a significant health problem. If your tongue is either of these colours, consult a health professional as soon as possible.
- A peeled tongue, sometimes called a "geographic tongue" because it looks like a map, can indicate a crisis point in a long illness
Always observe the tongue in good daylight and exclude obvious false phenomena such as a purple tongue after sucking a blackcurrant lolly or a red tip after burning it on a hot drink.
