Back Acne- Glycolic for Pigmentation and Scarring. The glycolic peel will help minimize and reduce pigmentation differences, as well as reduce the appearance of scarring while smoothing the skin and encouraging collagen growth. Normally a series of 6-8 weekly treatments is required to notice full results, as the improvements are incremental. The Benefits of Lactic Acid. For primarily pigmentation, I would the lactic/50 peel, or for pigmentation and scarring the glycolic 30 is best and for active acne, salicylic 20. There are a few things to keep in mind while applying to your back. We recommend applying in the shower (with the water off), or next to the shower to ensure you can remove it easily and thoroughly. Also, application of the peel will be much less troublesome with the aid of another person to ensure you can remove it easily and effectively. The salicylic peel will also be effective for acne on the back, you may even rotate between glycolic and salicylic for best results.