Back in 2023, a 64-year-old man experienced something weird. He had green hair growing on his tongue. Initially he was prescribed antifungal medicine, however, the treatment did not work on him. What he had was called a hairy tongue. A Visit To DocThe patient's tongue turned green about two weeks before he paid a visit to the doctor. This was shortly after he had completed a course of antibiotics from a gum infection. What initially happened was a discoloration and doctors thought that it was a case of oral thrush, which is a fungal infection. As a result, he was prescribed antifungal treatment, however, this did not do anything. Rather, there was moss-like growths.When doctors had a closer look, they realized that the man's filiform papillae, which are the tiny, cone-shaped bumps that cover the surface of the tongue and give its rough texture were longer than from a healthy tongue. Though there were no signs of injury or change in taste reported from the patient. What The Case Report Said?The case report was published in the New England Journal of Medicine, where physicians wrote, "A diagnosis of hairy tongue was made."What is hairy tongue? Hairy tongue or lingua villosa is a benign condition that causes hair-like growths of various colors to sprout on top of the tongue, said the report. These growths are filiform papillae that haven’t shed as they normally do through regular friction — such as from brushing with a toothbrush, using a tongue scraper, or eating solid, textured foods. Under typical conditions, these tiny projections grow to about 1 millimeter before falling off naturally, in a process called desquamation, similar to how skin sheds, according to the Cleveland Clinic.When this natural shedding doesn’t occur, the papillae can continue growing—reaching lengths of up to 0.7 inches (18 millimeters)—which can result in a condition known as hairy tongue. According to the American Academy of Oral Medicine, it affects roughly 13% of people at some point in their lives, most commonly in men and individuals over the age of 65.As these bumps elongate into hair-like strands, they begin to trap food particles, bacteria, dead skin cells, and other debris—leading to the discolored, furry appearance of a hairy tongue. According to the American Academy of Oral Medicine, the tongue may appear brown, white, green, or even pink, depending on the underlying cause and factors like mouthwash use or certain candies.What Causes Hairy Tongue—And Why It Sometimes Turns Black or GreenIn many cases, hairy tongue takes on a jet-black appearance, a condition medically known as lingua villosa nigra, or black hairy tongue, according to a recent case report.Several factors can increase the risk of developing a hairy tongue—regardless of its color. These include consuming a soft-food diet, drinking excessive amounts of coffee, tea, or alcohol, smoking, dehydration, poor oral hygiene, and taking certain oral medications that alter the mouth’s microbial balance. Regularly brushing the tongue is one of the most effective ways to prevent the papillae from becoming elongated and discolored.In the case report, doctors treated a patient who presented with a green-colored tongue. They advised him to gently scrub his tongue with a toothbrush four times a day and to stop smoking. At a six-month follow-up, the patient’s tongue had returned to a normal appearance—even though he continued to smoke, the report noted.