After VBeam Perfecta 1 treatment yesterday, what can I do to lessen under-eye swelling? (Photo)

Icing helps along with head elevation.  But there is nothing more you can do but wait a few weeks.  Benadryl at night and zyrtec or allegra during the day will not hurt, but I am unsure how much they will help.  If it is very severe and you are worried, consider going to your physicing for an evaluation and he can give you a corticosteroid injection or oral prednisone for a few days.  Best, Dr. Emer.

It seems you were treated fairly aggressively. I occasionally get swelling, but that's usually when combined with filler around the eyes. Head of bed elevation and ice should help. Steroids can be added to expedite the resolution.