Why scars never completely disappear from the human body

Although many people expect them to disappear over time, scars are designed to remain. Far from being a defect, they are the result of a body's defense mechanism that prioritizes protection over the aesthetic regeneration of the skin.

According to Corey Maas, associate professor at the University of California, San Francisco and cited by Popular Science, this tissue fulfills a key function: it acts as a barrier against external aggressions, ensuring the integrity of the organism even if that implies leaving a permanent mark.

Although they may fade over time, scars do not disappear completely. After a deep wound, the body replaces the damaged area with scar tissue rich in collagen, designed to close and reinforce the affected area.

This material is resistant, but it does not reproduce the properties of the original skin: it lacks sweat glands and hair follicles, and its fibers are organized differently, which prevents it from fully integrating with the surrounding tissue.

It is worth noting that human skin is the largest organ in the body and is composed of three fundamental layers. The outer layer is the epidermis, followed by the dermis and, finally, the inner layer called the hypodermis. According to Dr. Maas, the integrity of these layers is essential to maintain the protective function of the skin. Its continuity allows the skin to act as an effective defense against microbes and other harmful elements, detailed Popular Science.

How a Scar Forms

The healing process begins immediately after an injury. First, the body generates a blood clot to stop the bleeding. Then, a scab is created to protect the wound during the initial stages of healing. Shortly thereafter, the immune system kicks in. It sends specialized cells to the affected area, which release "citokines", molecules that coordinate the defensive response and alert the rest of the organism to contain potential infections. Later, the fibroblasts —key skin cells— release extracellular matrix. This substance is made up of long fibrous proteins, mainly collagen, which provide rigidity and resistance to scar tissue. The superficial closure of the skin can occur in a few days, but the complete reconstruction of the internal layers can extend for months or even years.

Why some wounds leave scars

Scars on the skin appear when injuries affect deeper layers such as the dermis or hypodermis (Illustrative Image Infobae)

Not all skin injuries end with a visible scar. If only the epidermis, the most superficial layer, is damaged, the skin usually regenerates without leaving any marks.

Instead, if a wound goes beyond the epidermis and affects the dermis or hypodermis, the body acts quickly to cover the area with new scar tissue. The main goal is to restore defense against the environment, and not to preserve the original texture or appearance. For this reason, deep cuts, severe burns, and injuries that compromise the inner layers of the skin almost always leave a permanent mark.

What makes scar tissue different

Scar tissue is distinguished by its composition and functionality. It is formed by dense bundles of collagen and connective tissue, but lacks sweat glands and hair follicles. This means that the scar does not perspire or produce hair, and cell turnover is low. As Dr. Maas explained to Popular Science, the collagen molecules that make up scars “are there forever”. That permanence explains why the difference between scar tissue and healthy skin is never completely eliminated. The organization of these fibers also differs, which gives the scar its own texture and color. Although they tend to flatten and soften over the years, their appearance is never identical to that of the rest of the skin.

What are keloid and hypertrophic scars

Sometimes, the natural healing process is excessive and generates anomalous lesions. Among the main types are hypertrophic scars and keloids. Hypertrophic scars and keloids arise when healing exceeds the body's natural process (Illustrative Image Infobae) Not all scars evolve in the same way, and some may become more visible or problematic over time. Hypertrophic scars, for example, are raised and reddened, but they stay within the limits of the original wound. Instead, keloids go a step further: they can expand beyond the initial injury, generate discomfort or pain, and even limit movement if they appear near a joint. According to Popular Science, their treatment also presents challenges, as surgical removal can cause them to reappear with a larger size.

How to care for a scar

Proper wound care influences the final appearance of the scar. According to Maas, it is essential to maintain cleanliness and, in the case of open wounds, cover them with new dressings to prevent infections.

If the wound is closed, it is recommended to apply a thin layer of ointment during the healing phase. Over time, the collagen deposits reorganize, allowing the scar to flatten and blend in part with the surrounding skin.

However, even with medical treatments, such as the use of steroids to reduce redness, it is not possible to completely erase the differences between scar and normal skin. The importance lies in the proper care after the injury to diminish the subsequent visibility of the mark.