"The inside of my mouth becomes inflamed. Could it be an allergic reaction? sensitivity? or a sign of some disorder?"
"The inside of my mouth becomes inflamed. Could it be an allergic reaction? sensitivity? or a sign of some disorder?"
"The inside of my mouth" 「口内」
"becomes inflamed" 「 腫れている」・「荒れることがある」"becomes swollen" も言えます。
"could it be an allergic reaction" 「[アレルギー](https://eikaiwa.dmm.com/uknow/questions/33333/)の反応可能性?」・「アレルギー?」
"sensitivity" 「弱い」
"or a sign of ~" 「〜の兆し」
"some disorder" 「不調」