A normal human tongue is pink to reddish in color, but a tongue that is considered "coated" often looks white, yellow or brown, and can feel "hairy." The cause of a coated tongue can vary widely, as can treatments for it.

Coated or 'Hairy' Tongue

According to the American Academy of Oral and Maxillofacial Pathology (AAOMP), the coated tongue known as a "hairy" tongue is usually due to short-term irritation--such as drinking a too-hot beverage--to the keratin cell layer on your tongue. Also, when the tongue does not shed keratin cells properly, you can actually feel the tiny "hairy" projections of keratin on your tongue.

Yellow-Coated Tongue

Yellow or brown-coated tongue is caused when tiny projecting papillae (known as taste buds) become irritated and enlarged due to smoking, dehydration and the effects of flu, fever and other types of nasal congestion, according to the Mayo Clinic.

Treating 'Hairy' or Yellow-Coated Tongue

According to the AAOMP, using a tongue scraper once a day to help remove dead keratin cells from your tongue and reducing irritants in your diet can help with a coated tongue. According to the Mayo Clinic, a mouthwash of one part hydrogen peroxide to five parts water may help "yellow" coated tongue, and quitting smoking is advised.

White-Coated Tongue

Other types of coated tongue have more serious causes. A white-coated tongue can indicate you have oral thrush or oropharyngeal candidiasis (OPC), according to the AAOMP.

Oral Thrush

Oral thrush occurs when the fungal infection candida albicans is present in your mouth, according to the Mayo Clinic. It is usually characterized by small whitish spots on your tongue and sides of your mouth. The candida must be treated to treat this type of coated tongue.

Source:

aaomp.org: American Academy of Oral and Maxillofacial Pathology on Hairy Tongue

MayoClinic.com: Information on White-Coated Tongue, Yellow Tongue and Oral Thrush