A man presented to his doctors with an unusual and slightly worrying symptom: his tongue had turned green and hairy. 

The 64-year-old had noticed the change to his tongue over the few weeks prior to his appointment at the clinic.

"On physical examination, the tongue had elongated filiform papillae and green discoloration. No other oral or dental lesions were noted," the man's medical team wrote in a case report. "A diagnosis of hairy tongue was made."

The harmless and fairly common condition's appearance is caused by a buildup of dead skin cells on the tongue. This causes papillae that coat the tongue, and contain tastebuds, to lengthen. In turn, the papillae trap other substances, such as food, bacteria, and yeast. The discoloration is frequently black, but can be brown, yellow or, as was the case here, green.

The condition can be caused by a rare side effect of antibiotics, poor oral hygiene, dry mouth, smoking, or eating a diet of soft food that doesn't rub off the dead skin on your tongue. The doctors note that this man had stopped taking antibiotics for a dental infection just prior to the onset of symptoms.

Fortunately, it is simply treated by removing the cause of the condition and good oral hygiene. The patient was advised to gently scrub at his tongue with a toothbrush, and quit smoking. Six months later, the doctors saw that his tongue had returned to its normal appearance, though the man continued to smoke.

The case study was published in The New England Journal of Medicine.