Scarlet fever: an infective condition distinguished by a red rash covering the whole body and a bright red tongue. (fitnessandpower.com)
A bright red tongue is a strong, almost unmistakable sign of an occuring infection and inflammation, especially when it's accompanied by the appearance of red dots. (fitnessandpower.com)
A bright red tongue could be a sign of not enough folic acid, vitamin B12, or iron. (health.com)