How long does it take for a raised scar to flatten after breast lift?

Hello! Thank you for the question! It is common for scars to fully mature for up to a year. In the meantime, there are a few things that may help to ameliorate your incision/scar. The most proven (as well as cheapest) modality is simple scar massage. Applying pressure and massaging the well-healed scar has been shown to improve the appearance as it breaks up the scar tissue, hopefully producing the finest scar as possible. Other things that have been shown to add some benefit, albeit controversial, are silicone sheets, hydration, and topical steroids. These can usually be started at approximately 3-4 weeks postop and when incisions healed. In addition, avoidance of direct sunlight to the incision will significantly help the appearance as they tend to discolor with UV light during the healing process. Scars will never disappear, but attempt is made to make the finest scar in a concealed location. Incisions may be revised to lower or conceal better if enough laxity exists. If unsightly scars are still present after approximately a year's time, other things that your surgeon may consider are intralesional steroid injections, laser, or just surgical revision of the scar itself. Hope that this helps! Best wishes!

Hello, first let me say that all scaring processes are different from each other, so don't be alarmed if both of the scars aren't completely the same. Second, it may take sometimes up to a year for a scar to become inactive, decreasing its color and flattening. Sometimes they stay like that and you would need further treatment for it to look better. 

As you noted on yourself, scars can mature at different rates, even on the same patient.  Each individual will have scars that mature at a different rate.  Most is due to genetics and others to surgical issues.  For all scars, time is on your side as nearly all scars get better with time.  Check with your plastic surgeon about some conservative measure to take, such as silicone pressure strips on your scar which may help the more active one to flatten and soften slightly faster.