Does Botox Affect Melasma?

Botox is injected into facial muscles and would not cause any hyperpigmentation.  Botox only affects the movement of facial muscles. Melasma or brown spots are not caused by Botox.  Injecting Botox will not make your hyperpigmentation worsen.  I would make sure to wear a hat and sunscreen.  Topical creams, chemical peels, IPL, and lasers are all a good options to lighten the pigmentation of the skin.  
Regards Anil Shah

Melasma is a common,  frustrating, chronic condition that is usually accompanied by much emotion. Thankfully, Botox/Dysport treatments will not exacerbate the condition. 
If you are struggling with melasma, you may want to view our many blogs on our website that serve as an educational source.

Thanks for your question -
Botox will not change melasma.  Botox directly interferes with the neuromuscluar junction.  Melasma is characterized by hyperpigmentation.  The pharmocologic action of Botox is completely unrelated to hyperpigmentation.
I hope this helps.

Botox has not exacerbated melasma. If a numbing cream is applied prior to the administration of Botox and should an irritation occur from this application, then melasma could be worsened. Any physical irritation or rubbing or sunexposure can worsen the melasma.

Melasma, or the 'mask of pregnancy', is discoloration or hyperpigmentation patches usually around the cheeks, nose, and upper lip. It is best treated or improved with cessation of oral contraceptives, intense pulse light lasers, hydroquinone or agents such as Cosmelan. Botox has no effect on melasma. Botox is a neurotoxin that will improve dynamic wrinkles by relaxing or temporarily paralyzing muscles.