Redness and Itching on Areas Untreated with TCA Peel

TCA at that strength should never be done by a lay person. In fact, even very experienced dermatologists rarely use TCA over 35%. The itch and redness are signals that something is wrong. You are at risk for post-inflammatory hyperpigmentation and scarring, so go see a board certified dermatologist ASAP and stop playing doctor before you scar yourself.

An "id" reaction, also known as "autoeczematization is an allergic-type reaction distant to the site of the stimulus (in your case, TCA peel solution). A similar reaction can occur in response to certain infections and poison oak or ivy. A short course of cortisone would be appropriate in this case. I hesitate to make a diagnosis without actually seeing someone in person. I suggest you seek the care of a dermatologist in your area.