A cracked tongue -- also known as a "scrotal tongue" or "lingua plicata" -- is a truly painful condition in which fissures cut across the surface of the tongue. A cracked tongue can also cause bad breath, since the cracks in the tongue become breeding grounds for anaerobic bacteria. In extreme cases, it can even become difficult to swallow or talk. There is no definitive cause for cracked tongue, but there are many possibilities.
The tongue is one busy organ. Eating, drinking, swallowing, kissing: the tongue has a lot more contact with the outside world than, say, your gall bladder. But this social nature comes with a price -- the tongue is exposed to many possible irritants, such as blistering drinks or spicy foods. Eventually, these could lead to a cracked tongue.
Ever accidentally bite your own tongue? Of course you have! Contact between teeth and tongue is not always so dramatic, but it is frequent -- over the course of the day, think about the number of times your tongue scrapes against your teeth. This friction, over time, could lead to a cracked tongue -- particularly if you have a rough or broken tooth.
Some toothpastes -- particularly those which contain alcohol -- have been known to cause cracked tongues. Be sure to rinse your mouth out completely with water before going to bed.
You've heard of nail bitters and hair pullers, but how about tongue chewers? It's more common than you think. Many people chew on their own tongue when under pressure, mostly during sleeping hours. You could be causing a cracked tongue in this manner and not even realise it.
Also, teeth grinding--another symptom of stress--has been known to cause cracked tongue. Moral of the story: relax!
This has never been proven conclusively, but some experts feel that cracked tongues can pass from parents to their children. Ask your parents if they suffer from cracked tongue as well.
See a Doctor
Although a cracked tongue is usually just an annoying irritation that will pass with time, it can be indicative of more serious conditions, such as cancer and diabetes. In order to be safe, your best bet is to see your family doctor or go to an ear, nose and throat specialist.