A hypertrophic scar is a thick, raised scar that forms when your body produces too much collagen during wound healing. Unlike normal scars that flatten over time, hypertrophic scars stay elevated and firm, often appearing red or pink. They’re common, developing in an estimated 32 to 72% of wounds depending on the type and location of injury.
The key feature that defines a hypertrophic scar is that it stays within the borders of the original wound. It may look alarming, but it won’t spread into surrounding healthy skin. Most hypertrophic scars eventually plateau after months of growth and then partially regress on their own, though this process can take a year or more.
What Causes Hypertrophic Scars
Normal wound healing involves your body laying down collagen to close a wound, then gradually remodeling that collagen into a flat, pale scar. In hypertrophic scarring, this process goes into overdrive. The wound-healing cells in hypertrophic scars produce abnormally high levels of a growth signal called TGF-β1, which pushes those cells to keep manufacturing collagen long after they should have stopped. The result is a dense buildup of collagen fibers arranged in tight, whorled bundles beneath the skin’s surface.
These overactive wound-healing cells also transform into a specialized type called myofibroblasts, which behave almost like tiny muscle cells. They contract the tissue around them, pulling the scar tighter and making it feel firm or ropey. Normally, these cells would die off once the wound closes, but in hypertrophic scars they resist the body’s usual cleanup signals. They survive longer, keep producing collagen, and break down less of it than normal cells would. This imbalance between collagen production and collagen removal is the core problem driving hypertrophic scar formation.
Who Is Most at Risk
Burn injuries carry the highest risk. Studies report hypertrophic scarring rates between 8% and 67% after burns, with the wide range depending on burn severity and the population studied. Surgical wounds are also a frequent trigger: nearly 60% of patients who underwent breast reduction or chest surgery developed hypertrophic scars in one study.
Several factors increase your likelihood of developing one:
- Skin tone. People with darker skin develop hypertrophic scars at roughly twice the rate of those with lighter skin. One early study found rates of 30% in dark-skinned patients versus 15% in white patients after burns.
- Age. Younger people are more prone, likely because their skin heals more aggressively.
- Sex. Women face slightly higher risk than men.
- Wound size. Burns covering more than 20% of the body significantly increase risk.
- Body location. Areas where skin is under constant tension are hot spots: the chest, back, shoulders, upper arms, and skin over joints like elbows and knees.
That last point matters because mechanical tension on a healing wound signals the body to reinforce the area with more collagen. Joints bend, chest skin stretches with breathing, and shoulders move constantly, all of which keep pulling at a healing wound and encouraging excess scar tissue.
How They Differ From Keloids
Hypertrophic scars and keloids are often confused because both are raised, thick, and result from abnormal healing. The single most reliable difference is growth pattern. A hypertrophic scar stays within or just at the edges of the original wound. A keloid spreads outward into healthy skin that was never injured, sometimes growing much larger than the wound itself.
Their behavior over time also differs. Hypertrophic scars typically reach a peak after several months and then begin to flatten and soften, at least partially. Keloids tend to keep growing without a clear plateau and rarely regress on their own.
Under a microscope, the two look quite different as well. Hypertrophic scars contain whorled bundles of collagen and abundant myofibroblasts. Keloids contain a distinct type of thick, glassy collagen (called keloidal collagen) and show structural features like a tongue-shaped advancing edge that pushes into surrounding tissue. These microscopic differences are present in 100% of keloid samples and absent in 100% of hypertrophic scar samples, making biopsy a reliable way to distinguish the two when the clinical picture is unclear.
What Hypertrophic Scars Look and Feel Like
A hypertrophic scar typically appears within weeks of a wound closing. It starts as a red or dark pink raised area that feels firm and slightly rubbery. Over the following months, it may continue to thicken and darken. The scar can itch, sometimes intensely, and may feel tight or uncomfortable, especially over joints where skin needs to stretch.
Pain is also common, ranging from mild tenderness to a more persistent aching sensation. The redness comes from increased blood flow to the scar tissue. Over time, as the scar matures, the color usually fades toward pink or pale and the texture softens, though this process can take one to two years and the scar may never become completely flat without treatment.
Prevention and Early Treatment
The strongest evidence for prevention centers on silicone. Silicone gel or silicone sheets applied to a healing wound after surgery or trauma reduce the likelihood of hypertrophic scar formation. Both formats work similarly, though silicone gel tends to be more practical for areas that move a lot or that you’d prefer not to cover with a visible sheet. It’s also easier to use consistently in warm climates where sheets can slide or trap heat.
Starting silicone early matters. If you’ve had surgery or a wound at a high-risk location (chest, shoulders, joints), applying silicone gel or sheets promptly after the wound closes gives you the best chance of preventing abnormal scarring. Silicone works primarily by keeping the scar hydrated and protected, which appears to calm the overactive collagen production that drives hypertrophic scarring.
Products containing onion extract are widely marketed for scars. The evidence suggests onion extract may help reduce redness, but silicone is the ingredient that actually drives scar flattening. A three-arm study comparing the two found the best results came from combining silicone with onion extract, though silicone alone outperformed onion extract alone for reducing scar height.
Treating Established Scars
Once a hypertrophic scar has thickened and isn’t responding to silicone alone, the most common next step is injections directly into the scar tissue. A corticosteroid is the standard choice, typically given every three to four weeks for several sessions. The injection delivers anti-inflammatory medication directly into the scar, slowing collagen production and softening the tissue. Combining the corticosteroid with a second medication that blocks cell growth tends to produce faster flattening and more lasting results than the corticosteroid alone, with manageable side effects like temporary pain or minor surface erosion at the injection site.
Laser therapy offers another option, particularly for reducing redness. Pulsed dye lasers target the blood vessels feeding the scar. One study found a single treatment improved scar redness and thickness by 57%, while two treatments pushed that improvement to 83%. Another study reported a 59% improvement in scar height and 76% improvement in redness. These results are encouraging, though most people need multiple sessions spaced weeks apart.
Pressure therapy, using fitted garments that apply steady compression to the scar, is commonly used after burns. It works by limiting blood flow to the scar and physically compressing the excess collagen. Pressure garments need to be worn for many hours each day over months to be effective, which can be uncomfortable, but they remain a standard part of burn scar management.
How Long Recovery Takes
Hypertrophic scars are not permanent in the way keloids often are. Most will improve to some degree over one to two years even without treatment, as the body gradually remodels the excess collagen. With active treatment, you can speed that timeline significantly and achieve a flatter, softer, less noticeable result.
The combination of early silicone use, injections for thicker scars, and laser treatment for persistent redness gives most people a meaningful improvement. No treatment erases a hypertrophic scar completely, but the goal is a scar that’s flat, pale, and comfortable enough that it doesn’t interfere with movement or daily life.