Some scars raise above the skin’s surface because the body overproduces collagen during healing. In normal wound repair, collagen fibers are laid down in an organized pattern and eventually remodel into a flat scar. But when that process goes wrong, specialized repair cells called fibroblasts keep churning out collagen long after the wound has closed, creating a thick, elevated mass of tissue. This overproduction is driven by a combination of genetics, prolonged inflammation, and physical forces acting on the wound.
How Normal Healing Goes Wrong
Wound healing happens in overlapping phases: inflammation, tissue rebuilding, and remodeling. During the rebuilding phase, fibroblasts produce collagen (mainly types I and III) to patch the gap left by the injury. At the same time, some fibroblasts transform into myofibroblasts, contractile cells that pull wound edges together. In a flat scar, this process winds down once the wound is sealed. The collagen gets reorganized over months, and the scar gradually softens and flattens.
In raised scars, this shutdown never happens properly. A key signaling molecule called TGF-beta binds to receptors on fibroblast surfaces and activates a cascade of internal signals that tell cells to keep producing collagen, keep multiplying, and keep differentiating into myofibroblasts. Normally TGF-beta activity tapers off. In raised scars, it stays elevated, essentially leaving the “build more tissue” signal stuck in the on position. The result is excessive, disorganized collagen that piles up above the skin surface.
Inflammation That Won’t Quit
One of the clearest triggers for raised scarring is inflammation that drags on too long. In typical healing, inflammatory cells do their job in the first days to weeks, clearing debris and fighting infection, then recede. When inflammatory cells remain abundant into the later remodeling phase, they keep releasing chemical signals that stimulate fibroblasts. Research consistently shows that an extended inflammatory phase correlates with more severe scar formation. This is why wounds that get infected, take a long time to close, or are repeatedly irritated are more likely to produce raised scars.
Hypertrophic Scars vs. Keloids
There are two main types of raised scars, and they behave quite differently. Hypertrophic scars stay within the boundaries of the original wound. They typically appear one to two months after injury, grow rapidly for about six months, then gradually regress on their own. Under a microscope, they have a nodular structure containing small blood vessels, fine collagen fibers, and contractile myofibroblasts. Those myofibroblasts are why hypertrophic scars often feel tight and can restrict movement near joints.
Keloids, on the other hand, grow beyond the edges of the original wound and invade surrounding healthy skin. They do not regress with time. Their collagen structure is fundamentally different: large, thick fibers made of tightly packed fibrils, surrounded by an amorphous material between cells. Keloids lack the contractile myofibroblasts found in hypertrophic scars, so they don’t cause the same pulling or tightening. But they’re harder to treat, and surgically removing them often triggers a new, sometimes larger keloid.
Why Location on the Body Matters
Raised scars are far more common in areas where skin is under constant tension: the chest, shoulders, upper back, upper arms, and over joints like elbows and knees. This isn’t coincidence. Mechanical forces acting on a healing wound directly stimulate fibroblasts to produce more collagen.
When skin is stretched, fibroblasts sense that force through a process called mechanotransduction. Stretch triggers specific proteins on the cell surface that convert physical tension into biochemical signals, activating pathways that increase cell proliferation, migration, and collagen production. Lab studies show that applying cyclic mechanical stretch to human skin fibroblasts causes them to ramp up collagen output significantly. Clinically, wounds running perpendicular to the skin’s natural tension lines (called Langer’s lines) have a higher incidence of raised scarring, while wounds parallel to those lines tend to heal flatter. This is also why surgical incisions on the sternum and wounds at joints, where skin constantly moves and stretches, are particularly prone to raising.
Genetics and Ethnicity
Some people are simply wired to produce raised scars. There is a strong genetic predisposition, supported by keloid cases appearing in twins and running through families in patterns consistent with inherited traits. Researchers have identified multiple gene regions linked to keloid susceptibility, including genes involved in collagen regulation and immune signaling.
Ethnicity plays a measurable role. Keloid prevalence varies dramatically by population: roughly 0.09% in England, 0.1% in Japan, 8.5% in Kenya, and as high as 16% in parts of central Africa. A UK study of nearly 1,000 patients found excessive scarring rates of 2.4% in Black patients, 1.1% in Asian patients, and 0.4% in white patients. Black patients also tend to develop larger keloids and are more likely to have multiple keloids. Where keloids form varies by ethnicity too. The chest is the most common location across all groups, but ear keloids are especially common in Black patients (33% of cases), likely reflecting the popularity of ear piercings combined with genetic susceptibility.
Other Factors That Increase Risk
Beyond genetics and wound location, several practical factors raise the odds of a scar becoming elevated. Burns are a major trigger, particularly deep burns that damage the lower layers of skin. Any wound that takes longer than two to three weeks to close has a higher risk. Wounds with tissue loss, jagged edges, or repeated trauma during healing are also more susceptible. Age matters as well: hypertrophic scars most commonly develop in people in their twenties and thirties, when the body’s healing response is most vigorous.
Surgical wounds can raise if they’re closed under tension, placed in high-movement areas, or if post-operative complications delay healing. Even piercings, tattoos, acne, and minor cuts can produce keloids in genetically predisposed individuals.
What Happens Inside a Raised Scar Over Time
Hypertrophic scars follow a fairly predictable arc. After appearing one to two months post-injury, they enter a rapid growth phase lasting about six months. During this time the scar may be red, firm, itchy, and increasingly elevated. After peaking, hypertrophic scars slowly flatten and soften, though this regression can take a year or longer and the scar may never become completely flat.
Keloids have no such timeline. They can continue growing for years, sometimes decades, after the original injury. They may become painful, itchy, or tender. Because the collagen inside a keloid is so dense and disorganized, the tissue feels harder than a hypertrophic scar and doesn’t respond to the natural remodeling process that flattens other scars over time.
Reducing or Preventing Raised Scars
Silicone gel sheets are one of the best-studied options for both prevention and treatment. They work by hydrating the scar surface and creating a protective barrier that appears to regulate collagen production. Studies report reductions of about 68% in scar height, 86% improvement in texture, and 84% improvement in color. They’re most effective when used early and worn consistently for weeks to months.
Pressure therapy, often used after burns, works on a similar principle: sustained compression limits blood flow to the scar and reduces the mechanical signals that drive collagen overproduction. Corticosteroid injections directly into the scar are a common treatment for both hypertrophic scars and keloids, working by suppressing inflammation and slowing fibroblast activity. For keloids specifically, injections are often preferred over surgical removal, since cutting out a keloid frequently causes it to recur larger than before.
Minimizing wound tension during healing is one of the most practical preventive steps. Surgical tapes or adhesive strips that hold wound edges together and reduce pulling forces can meaningfully lower the risk of a raised scar. Keeping wounds clean, moist, and protected from repeated trauma also helps by preventing the prolonged inflammation that feeds excessive scarring.