Patchy discoloration after BBL(3 weeks post, 1 week post touchup) - What can I do to fix this extreme patchiness? (photo)

Hyperpigmentation from any type needs a combination approach of peels like cosmelan,  lasers like clear and brilliant and aerolase or laser genesis, radiofrequency like venus viva, and constant skin care and sun protection.  Bimontly facials with silk peel dermalinfusion is essential to hydrate, exfoliate and infuse vitamins and antioxidants into the skin.  If you have acne you can do additional treatments and peels to get more improvement.  I suggest a formal consultation with an expert in lasers and peels. Best, Dr. Emer.

Thanks for you question and posting a picture.  I'm sorry this happened to you.  Sun protection is essential year round, but especially before and after any device treatment.  It looks like the BBL settings were a little aggressive and you may have missed your sun screen application along your hairline.  Going forward, quality sun screen every day.  Our patients love EltaMD's tinted sun screens.  Work with your physician.  He sounds like is going to try to fix it.  If he can't with his options, look for a PicoSure laser in your area.  We have been very successful using the PicoSure laser with the FOCUS and / or Flat Lenses eliminating hyperpigmentation with a series of treatments.  FOCUS lens treatments have the extra benefit of reducing the underlying scar tissue.  This is one of our go to treatments for patients older than 40 and worried about the signs of aging.  This laser is safe for all skin types.  Start with sunscreen every day!  Once you have treated your hyperpigmentation to your satisfaction, you will probably need a follow treatment every 6 to 12 months depending your level of re-pigmentation.  Best of luck.

There are multiple causes for the patchy discoloration after BBL. If the area feels gritty, it migh flake off and improve. A gentle exfoliating scrub may help. If the patchiness is delayed and the area is smooth, it could be post-inflammatory hyperpigmentation. It can be improved with bleaching creams (prescription strength hydroquinone), topical vitamin C, light glycolic acid peels and strict sun avoidance. You need to use sunscreen with zinc and iron oxide or wear a hat. The pigmentation might last a few months. 
Best wishes. 
Razieh Soltani, MD, board certified dermatologist