Collagen is the most abundant protein in the human body, serving as the primary structural scaffold for skin, tendons, and connective tissues. When the skin suffers an injury, the body immediately begins a coordinated repair process. This repair relies on collagen deposition and organization to replace the damaged tissue. Understanding the visual appearance of collagen at different stages of healing helps distinguish between a normal healing wound and one that may develop complications.
Collagen’s Role in Early Wound Structure
The visual appearance of a healing wound during the proliferative phase is characterized by the formation of granulation tissue. Granulation tissue is a sign of active healing, and its beefy red, moist, and bumpy texture reflects the work of newly deposited collagen. This tissue is highly vascular, containing a dense network of blood vessels, which makes it look red and prone to bleeding upon slight contact.
The initial structural protein laid down by fibroblasts is predominantly Type III collagen, which is weaker and more disorganized than the collagen in healthy skin. This collagen forms a loose, delicate matrix that provides a temporary framework for the wound bed. The bumpy, “cobblestone-like” surface of the granulation tissue is caused by capillary loops intertwined with this newly formed collagen. Although structurally weak, this early collagen quickly fills the tissue defect and supports the growth of new blood vessels.
The Appearance of Mature Collagen Tissue
As the wound progresses into the remodeling phase, the tissue changes dramatically, moving from a vibrant red to a paler hue. This transition results from the collagen matrix being strengthened and reorganized, a process that can take months or years. During this time, temporary Type III collagen is gradually broken down and replaced by stronger, long-stranded Type I collagen.
Type I collagen is dense and organized into bundles that run parallel to the skin’s surface, unlike the basket-weave pattern of uninjured skin. The developing scar loses its red color due to a natural reduction in blood vessels, a process called vascular regression. This decrease in blood flow causes the mature scar to appear flatter, firmer, and paler than the surrounding healthy skin. The final scar tissue regains 50% to 80% of the original skin’s tensile strength, with its pale color and smooth texture reflecting the underlying, highly organized Type I collagen bundles.
How to Identify Abnormal Collagen Scarring
Pathological scarring results from an imbalance in collagen production and breakdown during the remodeling phase, leading to excessive tissue accumulation. Both hypertrophic scars and keloids are the main types of abnormal scarring and involve an overproduction of Type I collagen, but they differ significantly in visual presentation.
A hypertrophic scar is raised, firm, and often red or pink. Its defining characteristic is that the scar tissue remains strictly within the original boundaries of the injury. These scars may thicken for several months but often stabilize, showing a tendency to flatten and fade over time.
In contrast, a keloid represents a more aggressive overgrowth of collagen that extends beyond the original wound margins, invading the surrounding healthy tissue. Keloids can be raised, lumpy, or ridged and may appear shiny, often ranging in color from red to dark brown. They typically develop months after the initial trauma and can continue to grow indefinitely, rarely regressing on their own. The keloid’s aggressive horizontal expansion is the most reliable way to distinguish it from a hypertrophic scar.