In general they are caused by large pimples that have often popped and caused damage to the skin . When the skin heals , it produces collagen but this extra collagen prodiution may not match the rest of the skin . Acne scarring is acommon side effect of pimples , leaving people with various levels of scarring ranging from light scarring and pigmentation to heavy pitted scarring. Treatments available at Dr Kora Aesthetics for acne scarring