Yuck! Blech! What causes dry mouth?

A dry mouth is like a dry wit. If you don't watch it, it can get you into serious trouble. That's why specialty breath fresheners are such a boon to humanity. They moisten mouths, reduce bad breath and keep us from causing olfactory offense. But wait - what causes dry mouth, anyway?

If you've ever fallen asleep with your mouth open, you know one answer. Mouth breathing, especially during sleep, is possibly the most common cause of dry mouth. At the very least, it's one of the severest causes, since individuals may sleep with their jaws wide open for as many as seven or eight hours at a stretch, leading to a seriously parched palate.

But this is just the tip of the iceberg. Ask an oral health expert what causes dry mouth, and they can give you a laundry list.

- Medications. Both the Mayo Clinic and the National Institute of Dental and Craniofacial Research (NIDCR) list medications, prescriptions or otherwise, as a prime cause of dry mouth. Antihistamines, decongestants and allergy medications are the usual suspects, since they are intended to dry out mucus membranes. But plenty of prescriptions are to blame, too, including some antidepressants, blood pressure medications and muscle relaxants, according to the Mayo Clinic.

- Aging. As we get older, our salivary glands gradually produce less and less moisture. It's a natural part of getting older, on par with the skin's sebaceous glands drying up. (Which is the reason you don't see elderly people with acne.) You've probably smelled some distinctly bad breath coming from your elders now and then. They may be in need of a specialty breath freshening mouthwash or, if they wear dentures, an oxygenating rinse.

- Smoking. No surprise here: the hot gases and thick smoke that pass over the tongue when tobacco is smoked can quickly make your mouth as dry as jerky.

- Anxiety. Ask someone who has to speak in front of a big crowd what causes dry mouth, and they'll probably tell you that anxiety does. Being nervous (at a job interview, for example) can dry out the palate and moisten the palms and armpits, leading to bad breath and a sopping wet shirt.

- Sjogren's syndrome. It's rare, but it's real. This disorder of the salivary glands and tear ducts can leave the mouth and eyes exceedingly dry. Recently, famed tennis star Venus Williams recently revealed that she suffers from Sjogren's syndrome.