How They Form, Causes, Treatment, and More

Scars are made of fibrous tissue that forms during the wound-healing process and leaves a mark on the skin after an injury has healed. As part of the body’s natural repair mechanisms, collagen-based scar tissue replaces damaged or wounded skin.

Although minor nicks or scratches on the skin’s top layer usually won’t leave a visible scar, most wounds and surgical incisions penetrating deeper into the skin will result in some cutaneous scarring. A wound healing without scarring (i.e., scarless healing) is rare.

This article covers how scars form, types of scars, and how to treat them.

How Do Scars Form?

Scars form as part of the natural wound-healing process. Scar formation is characterized by four stages that occur on a predictable timeline, as follows:

1. Hemostasis (up to several hours after the injury): Hemostasis (blood clotting) stops the bleeding immediately after the skin is wounded. As the blood clot dries, its fibrin hardens into a protective scab, which creates netlike scaffolding that facilitates later wound healing and scar formation stages. 
2. Inflammation (one to three days after injury): Inflammatory reactions trigger the release of cytokines such as epidermal growth factor (EGF), which attract skin-healing cells like fibroblasts, neutrophils, and macrophages to the injured area. 
3. Proliferation and contraction (four to 21 days after injury): During proliferation, fibroblasts synthesize into an extracellular matrix (ECM), mostly made of collagen. The ECM provides structural support as injured skin is replaced by collagen-based fibrous scar tissue. Contraction also occurs as specialized cells called myofibroblasts pull the edges of a wound closer together, condensing the area where a permanent scar will form.
4. Remodeling (three weeks to one or two years after injury): The final stage of wound healing and scar formation is called remodeling or the maturation phase. During this phase, loose and relatively weak collagen from earlier phases of wound healing is gradually replaced by stronger and more flexible collagen, which makes scar tissue more compatible with surrounding unscarred, healthy skin tissue. Remodeling can last up to two years.

What Are the Types of Scars?

There are many types of scars, including:

• Flat scars: May appear slightly raised and will flatten and change color as it heals, eventually ending up slightly lighter or darker than the surrounding skin.
• Raised scars: These rise above your skin’s surface and can restrict your movement if they occur on a joint. They can appear after surgeries.
• Depressed scars: These appear below the skin’s surface, giving it a sunken, pitted look that may occur on the face due to severe acne or chicken pox.
• Keloid scars: When excess collagen creates a raised scar that extends beyond a wound’s original boundary, it’s called a keloid scar. Not everyone is genetically predisposed to keloid scarring.
• Contracture scars: These are scars that cover a large surface area and cause skin to tighten in ways that may restrict movement. They are often caused by burns.
• Stretch marks (striae): Pregnancy or rapid weight changes can cause the skin to stretch or shrink rapidly, which causes “stretch marks,” linear scars known as striae distensae.

Are There Signs a Scar May Form?

Whether a scar forms depends on several factors, including:

• Skin type
• Injury type
• Direction of wound
• Where on the body the injury occurred
• Age
• Nutrition

What Causes Scars?

Anything that punctures the dermal barrier and wounds either of the two layers of skin below the epidermis—known as the dermis and hypodermis—can cause scars. Age increases the odds of a skin injury causing a scar.

How Common Are Scars?

Scars are extremely common. Anyone who has ever cut or injured their skin probably has at least one scar. A 2022 international study involving 11,000 people found that 22% of respondents had a fresh scar less than one year old somewhere on their skin.

Do Scars Fade, Shrink, or Move Over Time?

Although scars rarely disappear entirely, they usually soften and fade over time. Avoiding excessive sun exposure and ultraviolet (UV) light will help a scar fade faster. Newly formed scars (those less than 18 months old) are highly susceptible to damage from the sun’s ultraviolet radiation, which can cause hyperpigmentation (patches of skin darker than the surrounding skin).

If treated properly, scars can shrink, flatten, and smooth out over time.

Related: How to Get Rid of Scars: Medical and Natural Remedies for Old Scars

Can Scars Be Treated?

Scars can be treated. Below are some scar treatments that can be used for facial scars or cutaneous scarring on other parts of the body.

Topical Treatments

Silicone-based creams, gels, or sheets are used to treat scars, and do not require a prescription.

Related: The 9 Best Scar Creams to Fade and Smooth Unwanted Scars, Tested and Reviewed

Steroid Injections

Steroid injections by a trained specialist or dermatologist can break down collagen and minimize the severity of raised hypertrophic and keloid scars. Injected corticosteroids may also help with scar prevention.

Radiotherapy

Radiotherapy uses low-dose X-rays as a radiation therapy for the treatment of keloid scars.

Dermabrasion

Dermabrasion, also called dermaplaning, resurfaces the skin with a rapidly rotating device that “sands” the outermost layer of skin. It’s used to treat different types of scars.

Filler Injections

Soft-tissue fillers can plump up the skin and make sunken atrophic scars that are depressed below the skin’s surface less noticeable. These are typically used to treat acne scars.

Microneedling

Microneedling is a nonsurgical procedure that punctures the skin with lots of tiny needles and may help improve the appearance of scars. Although some forms of microneedling can be done at home, it’s best to have a trained clinician or dermatologist perform this minimally invasive procedure due to the high risk of infections from unsterilized needles.

Cryosurgery

Cryosurgery, also known as cryotherapy or cryoablation, is a minimally invasive medical procedure that uses extremely cold temperatures to treat keloids and hypertrophic scars.

Surgery

Scar removal surgery, also known as scar revision surgery, is a surgical procedure that can improve a scar’s appearance and restore movement if it’s being impeded by scar tissue.

Laser Treatments

Laser therapy cannot completely get rid of a scar, but it can lessen its appearance by making the scar blend in more with with skin around it.

How to Prevent Scars

Although it’s not always possible to prevent scars from forming after your skin has been injured, below are ways to optimize the healing process and minimize scar severity:

• Prompt wound care: Immediately after a skin injury, wash the wound with mild soap and water to clean out infection-causing germs and debris. Applying antibacterial ointment may help minor cuts or scrapes heal faster with less scarring, but it shouldn’t be used on deeper wounds.
• Cover injured skin: Always cover a fresh wound with a sterile bandage to keep it clean and moist. Change traditional bandages and gauze dressings daily or whenever they get wet or dirty.
• Keep wounds moist: Hydrocolloid gel bandages keep wounds moist and prevent scabs from getting crusty; they can and should be worn for many days in a row. Vaseline (petroleum jelly) also keeps minor cuts moist, promotes healing, and may improve a scar’s appearance.
• Do not pick scabs: The longer an original scab stays attached to its wound site, the better. Picking scabs disrupts the wound-healing process and can cause more severe scarring. Resist the urge to scratch or pick a scab; waiting for it to fall off naturally can help prevent scarring.
• Avoid sun exposure: Keeping wounded skin and newly formed scars out of the sun will promote faster healing, reduce hyperpigmentation, and help them fade faster.

When to Contact a Healthcare Provider

Contact a healthcare provider if you have any concerns about how a wound is healing or notice signs of infection, such as redness, inflammation, warmth, or pus.

Some scars restrict movement and can reduce mobility. Scars can also take a psychological toll. Speak to a healthcare provider about scar treatment options or removal if a scar is disrupting your quality of life or impacting your mental health. 

Summary

Scars are a natural part of the skin’s wound-healing process. Most injuries that penetrate the dermis below the top layer of skin will leave a scar. There are many types of scars.

Keeping wounds clean, covered, and moist can reduce or prevent significant scarring. Avoid sun exposure and overusing hydrogen peroxide when your skin is healing. Scar treatments range from over-the-counter topical treatments like silicone sheets to medical procedures like steroid injections or surgical scar removal.