What Causes Severe Red Blotches In A 17 Month Old Baby?

hi. my 17month old daughter has really bad red blotches over her body. they dont seem to be annoying her. but this morning she has awoken with what looks like a really bad scald on her face (pure red and hot) but its not a burn. the rest of her body is still all red blotches. some spots all over her too. she is on an antihistomin. and steriods. ??