Hypertrophic Scar

A hypertrophic scar is a thick, raised scar that develops when your body produces too much collagen during the healing process. Unlike normal scars that fade and flatten over time, these scars remain elevated and can cause itching, pain, and movement restrictions, though they typically stay within the boundaries of the original wound.

Table of contents

• What is a hypertrophic scar?
• Difference between hypertrophic and keloid scars
• Where hypertrophic scars commonly occur
• Causes and risk factors
• How hypertrophic scars look and feel
• When hypertrophic scars develop
• Treatment options
• Prevention strategies
• Outlook and recovery

What is a hypertrophic scar?

A hypertrophic scar is a thick raised scar that forms as an abnormal response to wound healing^[1]. When your skin is injured deeply enough to affect the dermis (the deeper layer of skin beneath the surface), your body responds by making collagen to repair the wound. Collagen is a protein that is thicker than regular skin tissue. Most of the time, this healing process creates a flat scar. However, sometimes your body makes extra collagen, resulting in a raised scar^[1].

Normally, a small wound to the top layer of your skin heals nicely, and new skin forms as the wound heals. With deeper wounds, the thicker, less flexible collagen tissue becomes a scar^[1]. The formation of a scar is the normal response to wounding in adults, but when regulation is unbalanced, less desirable scars such as hypertrophic scars can occur^[3].

Difference between hypertrophic and keloid scars

The key visible difference between hypertrophic and keloid scars is how far the scar spreads around the original wound. With hypertrophic scars, the extra tissue that forms stays within the original wound area. With keloid scars, the extra tissue extends beyond the original wound area and can grow very large^[1].

Hypertrophic scars are pink to red in color, while keloids tend to be red to purple. Hypertrophic scars develop one to two months after injury, whereas keloids can take months to years to appear^[1]. Another important difference is that hypertrophic scars may become less noticeable with time and can improve naturally over one to two years^[2][4], while keloids never go away without treatment^[1].

When examined under a microscope, the collagen fibers in hypertrophic scars are arranged parallel to the upper skin layer, whereas in keloids, the collagen fibers have a random, disorganized arrangement with more blood vessels present^[1]. Hypertrophic scars are also generally easier to treat than keloids, which have a high return rate after treatment^[1].

Where hypertrophic scars commonly occur

Hypertrophic scars are more common in areas of the body where your skin is taut (stretched tight), such as your back, chest, shoulders and upper arms, elbows and other joints^[1][9]. They are particularly prone to develop in areas of high skin tension, such as the front of the elbow or back of the knee^[21].

However, hypertrophic scars can occur anywhere on your skin where you have had a skin injury or wound^[1]. Scar tissue can form from skin injury or wounds resulting from accidental trauma, inflammation, burns and surgical incisions^[1].

Causes and risk factors

Hypertrophic scars arise from injury to the skin that goes deep enough to affect the dermal layer. They can occur after burns, surgery, insect bites, tattoos, acne, chickenpox, and piercings^[3][7]. The specific mechanisms remain not fully understood, but several factors are thought to influence their formation.

In certain people, body cells called myofibroblasts produce too much collagen during healing^[7]. This can happen simply as a result of a person’s skin type and healing tendencies. More commonly, overproduction of collagen occurs when a wound is infected or inflamed, under a great deal of tension or motion such as in injuries over a joint, or left to heal without stitches^[7].

Several factors increase the risk of hypertrophic scarring. Mechanical tension on a wound has been identified as a leading cause^[4][3]. Burn wounds, especially second and third-degree burns, significantly increase risk^[1]. Systemic inflammation has been suggested to increase the risks by increasing inflammatory markers in the body^[3].

People between the ages of 10 and 30 years old are more likely to be affected, believed to be because young people have more elasticity in their skin and produce collagen at a higher rate^[17]. Unlike keloids, hypertrophic scars are less likely to be associated with skin pigmentation and affect men and women from any racial group equally^[9].

How hypertrophic scars look and feel

Hypertrophic scars typically appear as reddish, itchy, firm, raised tissue that is thicker than usual^[2]. They are often pink to red in color and can be uncomfortable and itchy^[5]. These scars are thick, red to brown in coloration, and may be itchy or painful. They do not extend beyond the boundary of the original wound^[4].

An active scar can be red, raised, firm and thick. Scars can become sensitive and limit motion and function^[21]. The scars are not dangerous or life-threatening, but they can be itchy and painful. More often they are simply a cosmetic issue, though some people seek treatment to minimize the appearance of the scar^[7].

Thick, tight scars may limit movement and can cause physical discomfort, delayed recovery, and aesthetic concerns, as well as long-lasting effects on a person’s self-perception and self-confidence^[20].

When hypertrophic scars develop

Hypertrophic scars usually develop within the first few months after an injury, typically appearing within one to two months^[1][9]. The scar healing process occurs in several phases. After the initial injury heals, the scar often becomes more reddened and enlarged over the following four to six weeks^[21].

Next, the wound becomes smaller and paler over the following several months. Later, the scar becomes soft and has a more natural color in most people^[21]. Hypertrophic scars often appear within a month of injury and continue to grow over six months. After that, they can stabilize or improve for up to one year^[21].

It can take a full year for a scar to mature. During that time, your body is remodeling and trying to improve the scar tissue on its own^[7]. Hypertrophic scars may improve naturally over time, although this process may take up to a year or more^[6]. They usually improve and fade over one to two years^[4].

Treatment options

Numerous methods have been described for the treatment of hypertrophic scars, but to date, the optimal treatment method has not been established^[12]. There is no single therapeutic approach that is best for all scars. The location, size, and depth of the lesion, the age of the patient, and the past response to treatment determine the type of therapy used^[15].

Most doctors will not treat an early hypertrophic scar because it can take a full year for a scar to mature. They typically ask you to wait several months to a year before starting any treatment^[7].

Corticosteroid injections are considered a first-line treatment for hypertrophic scars^[7][9]. Injecting a steroid into the scar every six weeks may help flatten and soften the scar. These injections can help break the bond between collagen fibers, softening the scar tissue beneath the skin and easing symptoms such as itching and pain^[24]. However, there is a limit to the number of times this can be performed, as the steroids may also weaken normal tissue around the scar^[7].

Silicone gel sheeting is a noninvasive, time-intensive, first-line option for prevention and treatment of hypertrophic scars^[9]. Silicone gel masks and sheeting have been used in treatment since the early 1980s^[17]. This treatment is best used at the very early stage of scar development. Pads are placed directly on the scar for 23 of the 24 hours in a day for between 6 and 12 months^[17]. It is believed that the silicone builds up water under the pad that helps keep the scar hydrated, which can help prevent worse scarring from forming^[17].

Pressure dressings or garments are effective for prevention of hypertrophic scars, especially in burns^[9]. This treatment works by applying compression to the wound and is often used for burn treatment. It has been claimed that the use of high pressure, elastic dressings can reduce the formation of hypertrophic scars by between 60 and 85 percent^[17]. Pressure dressings work by limiting the blood, oxygen, and nutrients to a wound, which reduces the rate of collagen production^[17].

Cryotherapy (using extreme cold to remove tissue) is useful for smaller lesions and in combination with other techniques^[9]. Cryosurgery may speed up the healing process of a hypertrophic scar to a flatter, paler appearance^[4].

Laser therapy is an approach that has been studied for treating hypertrophic scars^[4]. Alternative options for refractory scars include pulsed dye laser and possibly radiation^[9].

Surgical removal of scars poses a risk unless combined with one or several of the standard therapies. When first-line treatments fail, combination therapy including surgery, silicone sheeting, and corticosteroid injections is an effective second-line option^[9]. Surgical revision may be considered after one year^[4].

Other treatment options include injections of verapamil, fluorouracil, bleomycin, and interferon alfa-2b, which appear to be beneficial for treatment of established scars and are reasonable alternatives to corticosteroids^[9][12].

Despite the popularity of over-the-counter herb-based creams containing onion extract, the evidence for their use is mixed^[9]. Limited clinical trials have failed to demonstrate lasting improvement with these products or topical vitamin E^[9].

Prevention strategies

Prevention is the first rule in scar therapy^[15]. It is not possible to completely prevent hypertrophic scars, so those with a history of them should inform their doctor or surgeon if they need surgery^[4].

Scar treatment begins with the physician or advanced practitioner closing the wound well. By preventing further skin injury and reducing tension during wound closure, the scar heals better^[21]. Close all surgical wounds with minimal tension. Incisions should not cross joint spaces and should follow skin creases whenever possible^[15].

Formation of scars can often be prevented if anticipated with immediate silicone elastomer sheeting, taping to reduce skin tension, or corticosteroid injections^[9]. Pressure garment therapy is a commonly used approach to try to prevent hypertrophic scarring after a burn, but the effectiveness of this approach is unclear^[4].

After a burn injury, survivors should avoid direct sunlight as much as possible. This means using an SPF of at least 30 at all times and reapplying regularly. Frequent moisturizing, including after showering, can ward off harmful itching cycles. Excessive itching can be detrimental to recovery progress^[20].

Outlook and recovery

Hypertrophic scars have a better outlook than keloid scars. They may become less noticeable with time and can improve naturally, although this process may take up to a year or more^[1][6]. They do not get bigger over time and may get better in 12 to 24 months without treatment^[2].

Scars change over time, where some will improve with time and others worsen, but no scar disappears entirely. Some scars can take up to a year to mature^[21]. How a scar changes over time depends on location, size, and type.

Hypertrophic scars are easier to treat than keloids and have lower return rates after treatment^[1]. While the scars are not dangerous or life-threatening, patients who have prominent scars may experience a reduction in their quality of life. They can feel anxiety in social situations and experience sadness or frustration in relation to their scar, causing stress^[21].

Early controlled exercise programs can prevent stiffness of nearby joints. Exercises keep tendons and nerves gliding under the skin^[21]. With proper treatment and management, many people can see improvement in the appearance and symptoms of their hypertrophic scars over time.