There is something to be aware of when using the mint on your face.

on your face 这个词组，已经暗示 using 的逻辑主语是 you。不用考虑主句，尤其主句是There be 存在句，此外，to be aware of 的逻辑主语也已经暗示出来了，是 you。以下三句都可以：

There is something to be aware of when you are using the mint on your face.

There is something to be aware of when using the mint on your face.

There is something to be aware of using the mint on your face.

又如这句， Having trained 的逻辑主语是谁的问题：

Having trained for five years before making her debut, there is no denying the black pink star's hard work ethic and dedication to her craft.
【翻译】在首次亮相之前，她已经接受了五年的训练，不可否认，这位黑粉明星勤奋的职业道德和对艺术的奉献精神。

我认为，介词短语 before making her debut，意思等于从句 before she made her debut，已经提供了 having trained  的逻辑主语是 she。即便这个介词短语本身，里面有 her，也足以暗示逻辑主语是 she。