Can anyone give me an idea why a skin bleaching cream used pre surgery would aid regaining pigmentation after surgery?

A dermatologist may school me on this, but we will often recommend hydroquinone pre op as well in patients that have darker skin to help prevent hyperpigmentation or darkening of the surrounding skin post operatively. This darkening happens because of inflammation, and the darker your skin, the more pigment you can make. Pretreating decreases the chance of this happening.A scar will go through many pigment changes as it matures, typically from red to white when it is completely healed. If your surrounding skin becomes darker from the inflammatory process, your scar may look more white in comparison. It is not a bad idea to use the hydroquinone, and I would encourage you to use good scar care (typically silicone gel sheeting, embrace, or a scar cream like biocorneum) after surgery for the best results. I encourage patients to use scar care for a minimum of 3 months after surgery, and preferably until the scars start to soften and fade.Best of luck with your surgery!