What is the reason for red rashes on tongue and in mouth.my mother facing this problem since last two years.what is the correct reason?please tell me.

Tongue rashes: Many possibilities. Perhaps your mother is allergic to something she places in her mouth e.g. Mouthwash, toothpaste, lipstick, some food, medication, chewing gum, gargle solution etc. Try eliminating possible irritants or causes of allergy. Make sure not on medicine or sleeping pills etc. That can dry the mouth. If over weight may have sleep apnea that restricts normal breathing.