What does it mean when there is a red patch without tongue coating on the tongue?

A red area on the tongue without coating may indicate central denuded tongue, which is usually caused by insufficient body fluids (yin deficiency) or excessive stomach fire. It may be accompanied by symptoms such as bad breath, burning pain in the epigastric region, and constipation. Alternatively, it could be geographic tongue, characterized by irregular desquamation of the tongue coating with elevated borders. This condition is typically due to spleen and stomach qi deficiency, and may be associated with symptoms such as fatigue, abdominal bloating, and loose stools.