1. White patches 

Oral thrush, an overgrowth of a naturally occurring fungus, often appears when the immune system is depressed. Babies, denture wearers, patients with cancer, HIV and other immune-compromising conditions, anemia and diabetes patients, smokers and dry mouth sufferers are all at a higher than normal risk of developing oral thrush. A course of antibiotics can also trigger an attack.

Canker Sores-A white spot on the tongue surrounded by a red, inflamed halo is probably a canker sore

Leukoplakia-White or grayish patches called leukoplakia.Wiping or scraping does not change their appearance or texture, which may be thick or hardened.

2. Black patches

A yeast infections, cancer therapies, diabetes,or poor oral hygiene.A condition such as hairy tongue can cause the entire tongue to turn black as well. Tiny black spots will start to appear across the tongue due to excessive use of tobacco, alcohol or antibiotics. This is caused by a fungus that grows across in small black patches across the tongue.

3. Red tongue

A deficiency of folic acid, B12 and iron cause redness in tongue or Geographic tongue . This condition, also known as benign migratory glossitis, is named for the map-like pattern of reddish spots that develop on the surface of the tongue. At times, these patches have a white border around them and their location on the tongue may shift over time.

4. Webbed tongue

Oral lichen planus is an chronic inflammatory condition that affects mucous membranes inside your mouth. Oral lichen planus may appear as white,  red, swollen tissues; or open sores. These lesions may cause burning, pain or other discomfort.

5. Tongue ridges

Teeth pressing into tongue.

Visit your dentist if you find any of these symptoms .