Source : Webster's Revised Unabridged Dictionary (1913)

Erythema \Er`y*the"ma\, n. [NL., fr. Gr. ?, fr. ? to redden, fr.
   'eryqro`s red.] (Med.)
   A disease of the skin, in which a diffused inflammation forms
   rose-colored patches of variable size.

Source : WordNet®

erythema
     n : abnormal redness of the skin resulting from dilation of
         blood vessels (as in sunburn or inflammation)