Is 12 J of Fluency Enough to Achieve Permanent Hair Reduction?

With darker skin types (higher Fitzpatrick levels), one of the keys to successful treatment is being conservative with settings to prevent post-treatment skin discoloration. One of the ways to do this is to use a wider pulse width (one of the parameters on the laser that should be tailored according to the patient). Another way to ensure safe treatment is to use a lower (yet still effective) energy/fluence.

On the Lumenis Lightsheer device to which you are referring, a fluence of 12J/cm2 is certainly high enough to yield permanent hair removal. As with any laser used for hair removal, you will need multiple treatments to achieve an optimal result. This is because - at any one point in time - each of your (hundreds of thousands of) hair follicles will be in one of several stages of the hair growth "cycle." (Appropriate) lasers only treat hair follicles that happen to be in their "active" growth stage of the cycle at the time of treatment.

People respond at different fluence levels, depending on hair color, size,  density, etc.  one way to know is if you have follicular edema, swelling around the base of the hair after a treatment, and if you feel a pinch or a sensation like hair being plucked.  This indicates the laser is working, and at or very near a therapeutic level.