Normal reaction to a pulsed dye laser treatment can include erythema (redness), soreness, and edema (swelling). A pulsed dye laser is typically used to treat scars or vascular birthmarks or tumors and helps to decrease the red discoloration of the skin.
Blistering to any laser treatment can be concerning for possible adverse side effects. Even ablative treatments (resurfacing treatments) usually do not produce blisters. Blisters can be a sign of either a treatment that was very aggressive, or possibly an infection or an allergy to topical treatments.
Bottom line, you need to be seen by your physician to receive proper diagnosis and treatment to help prevent the situation from worsening.