Scar formation is a natural part of the healing process that occurs when the skin repairs wounds caused by an accident, surgery or disease. Scars are formed by the over-production of a naturally occurring chemical in the body called collagen.
In the normal healing process, collagen stops being produced once the wound has healed and the skin returns to normal. The time the skin takes to heal will vary depending on the degree of damage, and the longer it takes to heal the greater the chance of a noticeable scar.
Normal scars will develop during the first 48 hours after the wound closes and fade within three months, whereas abnormal scars can occur up to 18 months later.
If you have acne on your skin, inflammation occurs around the affected area. The skin needs nutrients to return to normal and heal. In this case, the blood vessels that proliferate around the area receive nutrients and the skin can be restored.
However, excessive proliferation can lead to caved acne scars or red acne scars(marks) and bumps by regenerating an excessive amount of collagen.