Allergy  过敏症
have an allergy to certain milk products
对某些奶制品有过敏反应

Flu  流感
I was too weak from the flu to work.
我因患流行性感冒身体虚弱不能工作.

Rash  皮疹
I break out/come out in a rash if I eat chocolate.
我一吃巧克力, 就出皮疹.

Have a fever  发烧
He had a slight fever.
他有点发烧。

Get a headache  头疼