Photodynamic therapy and skin peeling, is this a normal side effect?

Your dermatologist will advice you - depending on the location. If its facial PDT, 48-72 plus hours, if its on the leg, one week. Really depends. Be guided by your dermatologist. All the best, Dr Davin Lim. Brisbane. Australia.

PDT is a good option for patients who have acne who want to try an alternative treatment course but its not particularly great at getting rid of blackheads. Blackheads usually require physical extraction and a cream program to prevent them from happening in the first place. 

This is a common question.  Most individuals note some degree of redness, tingling or peeling during or after the procedure.  However, different patients metabolize medications at different rates.  The persistence of your dry patch is definitely something your dermatologist wants...