what is a tca chemical peel
1 Trichloroacetic acid (TCA) is the main peeling agent used for medium peels, though the peel may also be done in several steps using a different chemical solution followed by TCA. 2  Deep peels penetrate several layers of skin and cause a second-degree burn of the skin.ow a medium peel is done. The technique used to do a medium peel is similar to that used for a superficial peel, but the chemical may be left on for a longer period of time. Medium peels are more painful than superficial peels, because the chemicals are stronger and they soak deeper into the skin.