Beta Hydroxy Acids (BHA) is great for clogged pores/blackheads. Alpha Hydroxy Acids (AHA) is for surface exfolation of dead skin cells. Some good BHA products are Trish McEvoy's BHA pads, Paula's Choice 2% or 1% (which gets alot of raves), and Vichy's Normaderm 4% (from canada). There are also a number of AHA products including Alpha Hydrox 12% souffle and second the Aqua Glycolic products, which are great. So used together, it can really improve your skin as long as you start off slow and let your skin get used to it (in case you're sensitive). There's an excerpt from an article that may be helpful:
Because AHAs and BHA work through chemical processes, they can penetrate the skin and produce better results than cosmetic scrubs, which work only on the exposed surface of the skin. And, there is no risk that AHAs and BHA will cause you to lose too much skin. Technically, there is a drop-off rate, meaning the AHA and BHA will exfoliate just the dead or damaged surface skin and leave the healthy skin alone. This is the main reason why you will see a drop-off in performance when using an AHA or BHA product. The dramatic results in the beginning of usage (when the thickened, discolored layers of skin are being removed) seem much more impressive than the results from continued use. This is to be expected, and it is important to note that continued use of an AHA or BHA product is required in order to maintain skin’s smooth, even-toned, healthy appearance.
The primary difference between AHAs and BHA is that AHAs are water-soluble, while BHA is lipid-(oil) soluble. This unique property of BHA allows it to penetrate the oil in the pores and exfoliate accumulated skin cells inside the oil gland that can clog pores. BHA is best used where blackheads and blemishes are the issue, and AHAs are best for sun-damaged, thickened, dry skin where breakouts are not a problem (Source: Global Cosmetic Industry, November 2000, pages 56–57).
In a couple of weeks, it also cleared up some stubborn teeny bumps on my forehead that I thought would last forever after trying other treatments.