The likely culprit: dehydration. 鈥淲hen you exercise, your fluid鈥攚ater fluid and also your blood鈥攊s shunted from your mouth, your stomach, your GI tract to your muscles,鈥 says , chair of USA Track and Field鈥檚 sports medicine and science committee. 鈥淪ome people get kind of dry in the mouth, other people get a kind of thickness.鈥
is 98 percent water; the other two percent is made up of various substances including mucus and electrolytes. If you鈥檙e dehydrated, your saliva can become a thicker, more concentrated mixture of those substances. That white ring around your lips, Adams says, is likely a combo of mucus and electrolytes, including salt.
How to keep from looking like a rabid dog? Obviously, stay hydrated. Drink when you鈥檙e thirsty, and bring extra fluid on longer runs. Also, try chewing gum. 鈥淲hen you chew gum, digestive enzymes are released in your mouth, making it more moist in there,鈥 and thinning out the mucus, Adams says.
The bottom line: Dehydration is probably causing your runner鈥檚 mouth, so stay on top of your fluids. Chewing gum can also help, but if you鈥檙e perfectly hydrated and continue to have bothersome mucus buildup, see your doctor to determine if something other than dehydration is the culprit.