We all develop a furry type of white coating on our tongue by the end of the day. This is considered normal and is largely composed of food particles, bacteria and saliva. It is easily remove by brushing of the tongue to reveal the underlying pink color of a healthy tongue. However, there are cases where coating of the tongue is considered abnormal and sign of disease.
Normal Tongue Color and Texture
The tongue is naturally pink to red in color with a rough appearance. The color is due to the blood flow within it while the roughness is due to tiny bumps known as papillae (singular ~ papilla). These papillae contain thousands of taste buds which can be stimulated by different chemicals that enter the mouth (mainly food and beverages). This rough surface also allows for food particles to adhere to it more easily.
The normal furry white coating that occurs on the tongue may be tinged a number of different colors. These range of colors is usually due to the foods and beverages that are consumed. For example, eating a strongly colored blue candy will color the tongue blue. These instances are not a cause for concern as it is not a sign of an underlying disease and usually there are no accompanying symptoms.
Abnormal Tongue Coating and Furriness
There are many possible causes of tongue discoloration with or without a furry appearance or sensation. Some of the more common and prominent causes of a tongue coating has been discussed below but these are not the only possible causative conditions.
Leukoplakia and Hairy Leukoplakia
Leukoplakia is a condition where white patches form inside the mouth. It cannot be removed with scraping. The exact cause is unknown but it is believed that it may be due to repeated exposure to irritant as it is often seen in tobacco consumers (smokers and chewers). These thick patches may become hard and some may be precancerous.
Hairy leukoplakia is similar to leukoplakia but tends to develop on the sides and on folds of the tongue. It presents largely the same as leukoplakia with a furry appearance, hence the term hairy leukoplakia. The condition is known to be linked to Epstein-Barr virus (EBV) infection. It is also associated with a weakened immune system.
Oral Thrush (Candidiasis)
Oral thrush is an yeast infection of the mouth usually caused by the Candida species of fungi, and specifically Candida albicans. It is a fairly common oral fungal infection in people with a weakened immune system and frequently seen with poorly managed diabetes and in HIV/AIDS.
Oral thrush typically appears as a creamy-white coating commonly described as looking like cottage cheese. It can be scraped but there may be bleeding as a result. The tongue is often sore and red. There may also be cracking at the corner of the mouth and a loss of sensation may also be present.
Lichen Planus (Mouth)
Lichen planus is an autoimmune condition where the immune system attacks the skin and mucus membranes of cavities like the mouth and vagina. Due to the immune action, there is inflammation in these areas. The exact cause is unknown but it is believed to be triggered by a viral infection, vaccines, certain medication and some toxins.
The skin lesions often appear as itchy flat bumps that are usually purple in color. In the mouth there are usually white spots or patches and painful ulcers (open sores) may form. This presentation in the mouth is consistent with the vaginal lesions seen in women with lichen planus.
Glossitis (Inflamed Tongue)
Glossitis simply means inflammation of the tongue and can be due to a number of different causes. Some of these causes include infections, injury (mechanical and chemical trauma), allergies, nutritional deficiencies and certain skin diseases that may extend to the inside of the mouth.
Apart from cases where the inflamed tongue may be due to conditions like lichen planus, there is usually no specific coating in glossitis. Inflammation causes redness and swelling of the tongue. This swelling may cause the tongue to become smooth and the change in its normal texture may be incorrectly perceived as a coating of the tongue.
There are a number of vitamin deficiencies that can cause tongue symptoms, and the most prominent among these micronutrients are the B-vitamins. As mentioned above, it may be related to glossitis that develops with these vitamin deficiencies. The most notable is with niacin, folate and vitamin B12.
These vitamins cause a strawberry red tongue and it should be differentiated from scarlet fever which causes a similar tongue presentation. With vitamin B2 (riboflavin), a purple discoloration of the tongue may be seen with a deficiency (ariboflavinosis).
A geographic tongue is a condition where there are smooth red patches on the tongue surface, usually with raised red borders. It is not usually considered as a disease because it is not associated with any other symptoms or abnormalities. The exact cause is unknown but it appears to be linked to genetic factors and psoriasis.
The smooth patches are due to loss of the papillae normally found on the tongue surface. Along with the red raised borders, it gives the tongue an appearance of “islands” like that on a map. The size, shape and location of these “islands” can change over time and there may be discomfort, pain or burning on the tongue.
Black Hairy Tongue
Black hairy tongue is a harmless condition where the tongue has a dark (brown to black) and furry appearance. It arises when the papillae are longer than normal thereby creating an environment where dead skin cells, food and beverages, bacteria as well as tobacco may become trapped.
It is these substances and microbes which cause the dark appearance. Apart from being harmless, it is also temporary and a few simple measures can prevent or minimize it. People who suffer with a dry mouth, tobacco users, antibiotic use that changes the normal mouth flora (yeasts and bacteria), using certain mouth washes and poor oral hygiene are some of the possible causes and risk factors.
Some of the images above have been sourced from the Dermatology Atlas Brazil.