Scars and stretch marks are formed by the damage of the dermal layers of the skin resulting from a variety of causes including, cuts, burns, acne, pregnancy, rapid growth or weight gain and surgery.  All scar tissue has the same collagen as the surrounding area but the composition of the scar is different to the surrounding normal tissue.  Normal collagen fibres form bundles with a basket weave effect that gives tone and strength to the skin.

Scars can take a number of forms:

Atropic scars are sunken scars where the dermis has been thinned and are common in acne suffers where they take various forms Rolling, Boxcar and Ice pick are descriptions of common types of atropic scars.

Keloid scaring results from excessive regrowth of collagen around the wound site which results in a raised scar formed from stiff bundles of collagen. Keloid scarring occurs more frequently in darker skin types.

Pigmentation scars are not really a scar and will fade in time if treated, they usually result from the trauma caused by severe nodular acne or a skin condition e.g. Impetigo.

Stretch marks are a type of atropic scar and happen when the skin is pulled by rapid growth or stretching. The rapid growth can cause the skin to over-stretch and break the fibres. The tears in the skin surface (dermis) allow the blood vessels below to show through, which is why stretch marks are often red or purple when they first appear.