Scar tissue is the body’s replacement material for damaged skin or organs. When you cut, burn, or otherwise injure tissue, your body can’t perfectly recreate what was there before. Instead, it patches the area with a dense, fibrous protein called collagen, laid down in a single direction rather than the basket-weave pattern found in normal skin. The result is a patch that looks, feels, and functions differently from the tissue it replaced. A fully mature scar only reaches about 80% of the original skin’s strength, and it never fully regains the flexibility, sensation, or appearance of undamaged tissue.
How Your Body Builds a Scar
Scar formation isn’t a single event. It’s the end product of a four-phase healing process that begins the moment tissue is damaged. These phases overlap, but each has a distinct job.
The first phase, hemostasis, happens within seconds. Blood vessels constrict and platelets rush to the wound, clumping together in a mesh of fibrin to form a clot. This stops bleeding and creates a temporary scaffold for what comes next.
Inflammation follows almost immediately. White blood cells flood the area, clearing out bacteria and dead cells. This is the phase responsible for the redness, warmth, and swelling you see around a fresh wound. It’s uncomfortable, but it’s preparing the site for rebuilding.
During the proliferation phase, cells called fibroblasts take over. These are the actual scar builders. They produce collagen and other structural proteins, filling the wound with new tissue (called granulation tissue) while the skin’s surface layer migrates across the top to close the gap. This phase is when you’ll notice a wound starting to shrink and a pink, slightly raised area forming.
The final phase, remodeling, begins around week three and can last up to 12 months. During this time, the body reorganizes the collagen fibers that were initially deposited in a random arrangement. Cross-links form between collagen molecules, gradually increasing the scar’s strength. By six weeks, the scar has regained roughly 50% of the original skin’s tensile strength. It continues strengthening from there but tops out at about 80%, which is why scars remain a permanent weak point.
Why Scar Tissue Looks and Feels Different
Normal skin contains collagen fibers arranged in a complex, interlocking pattern, along with hair follicles, sweat glands, and elastic fibers that let skin stretch and bounce back. Scar tissue has none of these. The collagen in a scar is aligned in parallel bundles, which makes it stiffer and less elastic. It also contains a higher ratio of one type of collagen relative to another compared to normal skin. Research has found that the higher this ratio climbs, the more noticeable and raised the scar tends to be.
Because scar tissue lacks sweat glands and hair follicles, the area won’t sweat or grow hair. It’s also typically less sensitive to touch, though some scars develop nerve-related pain or itching. The color difference you see, whether paler or darker than surrounding skin, comes from changes in blood supply and pigment-producing cells in the repaired area.
Types of Scars
Not all scars look the same. The type you develop depends on how much collagen your body produces, where the injury is, and your genetics.
- Normal (flat) scars start out pink or red and gradually fade to a thin, pale line over months. They sit level with the surrounding skin and are the most common outcome of routine cuts and surgical incisions.
- Hypertrophic scars are raised and firm, but they stay within the boundaries of the original wound. They typically appear within four to eight weeks after the wound closes, grow over the next six to eight months, then stabilize. Many eventually flatten on their own over a period of years.
- Keloids grow beyond the edges of the original wound, sometimes significantly. Unlike hypertrophic scars, keloids can develop anywhere from three months to several years after an injury, rarely mature or stabilize, and tend to keep expanding. The key diagnostic difference is simple: if a raised scar is spreading past the wound borders, it’s a keloid. If it stays within them, it’s hypertrophic.
- Atrophic scars are the opposite problem. Instead of too much collagen, the body produces too little. The result is a sunken or pitted area below the level of surrounding skin. Acne scars are the most familiar example. The indentations form because inflammatory chemicals break down collagen fibers and underlying fat during the healing process, leaving a deficit rather than an excess.
Internal Scar Tissue and Adhesions
Scar tissue doesn’t just form on the skin’s surface. Any time internal tissue is cut or damaged, whether from surgery, infection, or injury, the same collagen-based repair process occurs inside the body. The internal version of scarring often takes the form of adhesions: bands of scar tissue that connect organs or tissues that aren’t normally attached to each other.
Adhesions are remarkably common after surgery. Studies report that 67 to 93% of patients develop adhesions after general abdominal surgery, with rates reaching as high as 97% after open pelvic procedures. Most adhesions cause no symptoms at all. But when they do, the effects can be significant: chronic pain, restricted movement of internal organs, bowel obstructions, and, in women, fertility problems caused by scar bands distorting the reproductive organs.
Internal scar tissue can also form in muscles, tendons, and joints after injuries or repetitive strain. This type of scarring can limit range of motion and cause stiffness or pain during movement, which is why physical therapy after injuries and surgeries focuses heavily on keeping tissues mobile during the healing process.
What Affects How You Scar
Several factors influence whether you develop a barely visible line or a prominent raised scar. Genetics plays a large role. People with darker skin tones are more prone to keloids, and a family history of abnormal scarring increases your risk. Age matters too: younger skin tends to produce more collagen, which can lead to thicker scars, while older skin often heals with thinner, more atrophic scars.
The location and direction of the wound also make a difference. Scars on the chest, shoulders, and earlobes are more likely to become hypertrophic or keloid. Wounds that run perpendicular to the skin’s natural tension lines tend to produce wider scars because the surrounding skin constantly pulls the wound edges apart during healing. This is why surgeons plan incision lines carefully when possible.
Wound care during the early healing phases has a measurable effect. Infections prolong the inflammatory phase, giving the body more time and reason to overproduce collagen. Wounds that are under tension, reopened, or left to heal without proper closure are also more likely to scar prominently.
How Scars Are Treated
Because scar tissue is structurally different from normal skin, no treatment can make a scar disappear entirely. But several approaches can significantly improve how a scar looks and feels.
Silicone gel sheets and topical silicone gels are among the most well-studied options. They work by increasing hydration in the outer layer of skin over the scar, which signals fibroblasts to slow down collagen production and helps restore a balance between collagen buildup and collagen breakdown. Research has documented an 86% improvement in texture, 84% in color, and 68% in height when silicone products are used consistently. Silicone also creates a protective barrier that prevents bacteria from triggering additional collagen production in the scar.
Pressure therapy, often using compression garments, is commonly used for burn scars. The sustained pressure reduces blood flow to the scar, which limits the nutrients available for excess collagen production. For raised scars, corticosteroid injections can shrink the tissue by suppressing inflammation and collagen synthesis. These are particularly useful for keloids that don’t respond to other approaches.
Laser treatments and microneedling work by creating controlled micro-injuries in the scar, triggering the body to remodel the existing collagen into a more organized pattern. These procedures are especially effective for atrophic (pitted) scars, where the goal is to stimulate new collagen production to fill in the depressed area. Multiple sessions are typically needed, and improvements develop gradually over months as the remodeling process unfolds.
For internal adhesions causing symptoms, surgical removal is sometimes necessary, though there’s an inherent challenge: surgery itself can trigger new adhesion formation. Barrier products placed during surgery can reduce this risk, and minimally invasive techniques produce fewer adhesions than open procedures.