The man had a stroke. After three months, his tongue became "hairy" and dark

A man in his 50s turned to doctors in India with a black hairy tongue after suffering a stroke, according to a report by JAMA Dermatology.

The man had left-sided weakness after a stroke that happened three months earlier, and he was transferred to a puree diet, doctors said in a report published on Wednesday. According to them, a thick black coating covered most of his tongue for about two weeks, sparing the lateral and middle parts.

Doctors diagnosed the condition as black hairy tongue, or lingua villosa nigra, a harmless condition, according to the American Academy of Oral Medicine. Hairy tongue is found in about 13 percent of the population, the academy says.

According to Indian dermatologists, black hairy tongue is more common in people who adhere to a puree-like diet, and is formed due to insufficient abrasion or stimulation of the upper part of the tongue, which leads to the accumulation of a protein called keratin.

As a result, the conical protrusions covering the tongue, called filamentous papillae, become long and form a kind of hair on the upper part of the tongue.

Other predisposing factors include: poor oral hygiene, smoking, oxidizing mouthwash, antibiotics, excessive consumption of coffee or tea, as well as diseases that suppress the immune system, such as HIV or cancer.

According to the National Institutes of Health, this disease can occur at any age, but is more common in older people.

A black hairy tongue can look brown, yellow or green, as well as black, according to the NIH, depending on the bacteria and fungi that can grow on the altered surface, as well as other anaerobic bacteria that ferment food particles stuck in the papillae. It is these anaerobic bacteria that give the tongue a black color.

Usually a black hairy tongue gets better if you brush your tongue with a toothbrush or use a tongue scraper.

In this patient, the disease passed after 20 days with "proper cleansing," the doctors said.