如果您想表示一个人有不好的胃，可以使用以下表达方式:

使用名词 "a sensitive stomach" 或 "a weak stomach" 来表示一个人的胃不好。

例句:

She has a sensitive stomach and can't eat spicy food.
(她胃较敏感，不能吃辛辣的食物。)
He has a weak stomach and gets sick easily after eating unhealthy food.
(他胃较虚弱，吃了不健康的食物后很容易生病。)
使用形容词 "nauseous" 或 "queasy" 来表示一个人感到恶心或不舒服。

例句:

The strong smell of the cleaning solution made her feel nauseous.
(清洁剂的浓烈气味让她感到恶心。)
The bumpy ride made him feel queasy.
(山路的颠簸使他感到不舒服。)

来源:

"sensitive stomach" 和 "weak stomach" 都是常用的俗语，没有固定的来源。
"nauseous" 源自拉丁文 "nauseosus"，意思是 "feepng sick to one's stomach"。
"queasy" 源自中古英文 "queas"，意思是 "feepng sick to one's stomach"。