When the skin is injured, the body mounts a significant response to try and get it healed as quickly as possible. When it comes to an incision, for instance, the body sends everything it has to get the cut closed. Once the incision has closed, it’s almost as if the body says “hey, I really overdid that”, and then spends the next year remodeling the scar until it looks good.
The same kind of thing happens with acne. As the body senses that the skin has been injured, it tries to “fix” it in several different ways. Which way it responds, and how aggressively it responds, depends in part on how much damage the body senses has occurred. If there is a small amount of irritation caused by the initial acne injury, it will heal without any scarring or discoloration. If the damage is more severe (i.e. if the injury goes deeper into the skin), it goes beyond the ability of the skin to heal without scarring and you can get anything from discoloration to scars. The scars can be deep, narrow scars (ice pick), wider round scars (boxcar), or in the worst case, there can be significant damage to the subcutaneous tissue which causes loss of thickness of the skin in a random uneven pattern causing the entire surface of the skin to roll up and down (rolling hill scar).
The scar tissue that forms at the bottom of the scar contracts as it heals, which tends to pull the bottom of the scar downward, causing the depressed appearance that we associate with acne scars. The treatment for these scars then depends on the appearance of the scar. The narrow, deep ice pick scars are usually treated with a punch excision. The punch is a small round cookie cutter type instrument that pushes through the skin around the scar, removing a narrow tube of skin that includes the scar. The edges of the skin left behind will heal together giving a better overall appearance. If the scar is a bit too wide to heal well, a small skin graft (a similar sized punch is taken from an area of normal skin where the scar will not be noticeable- behind the ear, for example) can be placed into the hole for a better result. If the scar is wider (boxcar), a punch elevation may work better. In this case the punch is used to cut around the edges of the scar and instead of removing the tube of skin in the middle, the tube is simply elevated upwards until it sits level with the surrounding skin. The scar is still there, but it is no longer depressed. Since it now sits flush with the surrounding skin, it is much less noticeable. Subcision is a technique where you are not removing or moving the skin at all. A needle is placed underneath a depressed area (usually coming in at an angle) and the sharp end of the needle is used to cut the fibers that are pulling the skin downward. As these fibers are released, the skin floats back upwards, giving a smoother appearance to the surface of the skin. This works best for areas that are depressed with relatively normal looking skin over the top. Fillers can be used for a variety of scars. They are injected underneath the scar, lifting it upwards. Fillers work best for scars that don’t have a lot of subcutaneous fibers tethering it downwards. Sometimes the combination of filler and subcision works well. Hyaluronic acid fillers work best for this (Restylane® probably works best because it doesn’t continue to draw water to it like Juvederm® does), although Radiesse® can be used if the scar is really stuck down. Micro injections of Botox® have recently been shown to smooth large pores on the skin and may be an option for some of the smallest acne scars. IPL is a great option for the discoloration associated with acne scars. IPL will remove the color from the scar, as well as decreasing the surrounding vascularity, making the scar the same color as the surrounding skin, and making it less noticeable. Finally, fractional lasers, both ablative and non ablative, have a role in the treatment of acne scars. Until recently, the ablative lasers were the most commonly used. They did 2 things. They removed the top layer of skin so that shallow scars were completely removed and deeper scars were made shallower. Second, they tightened the skin overall, which narrowed the diameter of the remaining scars. Non-ablative fractional lasers more recently have been shown to help reorganize the scrambled collagen in scars, making them smoother and softer. Last year, SkinMedica™ released a product called Scar Recovery Gel, that has some promise. Recognizing that early scar formation is characterized by too much type 3 collagen and not enough type 1 collagen (which is partly why early scars don’t look good), and mature scars (which look better) are composed of more type1 collagen and less type 3 collagen, Scar Recovery Gel pushes the skin to make more type 1 and less type 3 collagen, making scars look better sooner. If applied early (within the first few weeks) the overall appearance of the scars seems to be much improved and is an exciting new possibility that may turn out to be very helpful.