I bought the travel size exfoliating duo which has the 2% bha, and the lactic acid/mandelic acid. In the three days that I've been using them (each x once per day), my skin is already very different and I love them. Previously used a glycolic once a day but this is amazing stuff. But it's expensive 😩. Is there any alternative that's cheaper and still effective, or do I just have to save?! I have fairly sensitive skin so am really wary of retinols, feel like I've found a too-expensive holy grail!