Her face broke out in a rash.

她脸上突然长出一片红疹。

《牛津词典》

She looked tired, and her face was flushed and sweaty. Her blood pressure was quite low, her heart was beating unnaturally fast and the rash now covered her body.

她现在看上去很疲惫，脸通红，满身是汗血压很低，心跳快的不自然，身上覆盖着皮疹。

youdao

The rash usually starts on the face and spreads to the rest of the body.

一般在面部开始出现斑疹并向身体其它部分播散。

youdao

The blotchy rash appears a few days later beginning on the face and spreading downwards over several days.

BBC: Merthyr measles outbreak inquiry

The blotchy rash appears a few days later, beginning on the face and spreading downwards to the rest of the body over several days.

BBC: Boy with measles

The most common symptoms are fever, cough, sore eyes and a rash that develops three or four days after the onset of illness, starting with the face and head and spreading down the body.

BBC: Measles outbreak confirmed in Lancashire by HPA