[Product Question] What is the difference between a salicylic acid spot treatment and any BHA exfoliant?

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I'm a skincare newbie, so please be gentle with me! I feel like the answer to this will be rather obvious, but I want to hear a technical explanation from someone who knows more than I do.What is the difference between a spot treatment containing 2% salicylic acid and a BHA exfoliant also containing 2% salicylic acid? Why shouldn't someone smear the spot treatment all over their face in place of the BHA exfoliant, assuming they moisturize properly afterwards?Thanks!
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Submitted by andoliveyou