High concentration TCA acid works by stimulating collagen and by inducing new "scar formation" to fill up the depressed scar.
However, there are different types of acne scar. It could be Icepick, Rolling or Box Scars. Not all treatments are suitable for every type of acne scar. It is important to get an accurate diagnosis and make sure that the treatments you get are individualised for your specific condition.
TCA CROSS might not be the ideal treatment of choice for Rolling and Box Scars. Their effectivity would be quite limited in this instance.
For those type of scars, I would personally recommend a combination of Subcision and Fractional CO2 Laser instead. That would yield better results and is more effective in improving their appearance.
