Other than how their tongue looks, most people with black hairy tongue don't have symptoms. The exception is when there is too much growth of the yeast Candida albicans, which can cause a burning sensation called glossopyrosis. Some people complain of a tickling feeling in the back of the roof of the mouth, a metallic taste , or nausea. In more severe cases, the condition may lead to a gagging feeling. Sometimes, food getting caught inside the extra-long papillae can cause bad breath.