Is Hyperpigmentation Due to Alexandrite Laser Permanent?

usually, hyperpigmentation, an increase in your true melanin, or pigment, occurs longer than a week after trauma, such as a burn.  If skin starts to exfoliate it may turn darker sometimes and look like pigment but in reality there is no post inflammatory hyperpigmenation.  When there is such pigmentation, it is often temporary but can last even more than a year.  Sun protection is very important and several prescription creams can help lighten this pigment. See a dermatologist for evaluation and treatment.

Before you spend $$ on peels or IPL, try these topicals.
This is called post-inflammatory hyperpigmentation (PIH). 
I recommend Melarase AM and Melarase PM creams from Kare Skin as well as a broad spectrum sunblock like Spectrase. Bothe are from Kare Skin. Scler-x post inflammatory hyperigmentation relief complex is a great supplement to take as well. See link below. 
Spectrase is a wide spectrum sunblock SPF 50+that is also recommended to prevent ongoing inflammation. 

Even though most of the time the pigmmentary changes (hypo or hyperpigmentation) are temporary, there is always a small risk that they may be permanent.

The skin typing of the patient must be done carefully, through a detailed questionnaire and any sun exposure to the area to be treated must be avoided for a month before and a month after each treatment.  The closer the color of the skin is to the color of the hair the more chances of complications.  Tanning makes the skin darker and must be avoided.