Would BBL make hypopigmentation worse? I am trying to treat dark spots on my face but I also have hypopigmentation areas.

Hello and thanks for posting your question. When used in the hands of an experienced provider, BBL is really quite safe and effective at reducing (and often eliminating) concerns relating to pigmented lesions, vascular issues (vessels, telangectasias, cherry angiomas, rosacea), and altering gene expression for maintaining more youthful skin. 
The thing that most patient concerns have in common is that the 'target' (brown spot, vessel....) has a 'color'. With respect to hypo-pigmented areas, depending on how depigmented an area is, its going to present relatively less 'target' and take up less of the light. It will take up some, and there's certainly a small possibility the area could 'clean up' a bit and look lighter, if in fact there is some subclinical (not as visible) sun damage present. The areas of more concern, or brown spots, can be targeted in a more focused manner and the treatment settings can be tailored to provide more effect. 
With a good provider, its likely the overall result will be pleasing to you. Do your homework and make sure you're in the hands of an experience provider!
Best,
Dr R

Hi Dear
Before any laser treatment you need to use sunscreen for one month also use some creams like Retin-A and hydroquinone to prepare the skin before any laser or BBL. If you don't prepare the skin there is a chance of pigmentation

Thank you
Ramtin Massoudi, MD