Retin a will increase collagen. There is usually minimal changes to scars in general. Pit scars are deep scars and you will not see any significant changes.
Hai...Retinoids increases the cell turnover. Hence the superficial layer of the skin is also turning over at a faster rate which mimics exfoliation. Usually a 'sunburn' kind reaction is experienced a few days post application. Hence it is advisable to soothen your skin with any kind of...
Retin A is available in several strengths. I find that there more affect with the stronger (0.1%) but the frequency and length of use is more important to collagen benefits.