How long does it take for Pulse Dye Laser treatment to show results?

It can take 6-8 weeks to see the results after a pulsed dye laser treatment.  And as you noted, it normally does take several treatment sessions to obtain the best results.

It can take a series of treatments to get improvement. I recommend following up with your cosmetic dermatologist for after care. I recommend PDT therapy to calm any inflammation.  I always combine lasers with microneedling/prp for best outcomes. See an expert. Best, Dr. Emer

It will certainly take several treatments to effectively break up the coloring in a port wine stain as those are very dense and concentrated. Normally we recommend treatments every 4-6 weeks to give the body time to break up what it can with each treatment. But you should be seeing some color changes and lightening already occurring. But you will definitely need several, several treatments. Port wine stains are not a one time treatment. "This answer has been solicited without seeing this patient and cannot be held as true medical advice, but only opinion. Seek in-person treatment with a trained medical professional for appropriate care."