Why scars never disappear

Science Ask Us Anything Why scars never disappear Scar tissue is built to protect, not vanish. By RJ Mackenzie Published Apr 28, 2026 9:08 AM EDT Add Popular Science (opens in a new tab) More information Adding us as a Preferred Source in Google by using this link indicates that you would like to see more of our content in Google News results. Scars protect the body quickly and efficiently after an injury. Image: Liliya Krueger / Getty Images Get the Popular Science daily newsletter💡 Breakthroughs, discoveries, and DIY tips sent six days a week. Email address Sign up Thank you! Terms of Service and Privacy Policy. I am a clumsy guy. If there are sharp corners nearby, I’ll bash into them. If there’s a surface underfoot with even a light sheen of polish, I’ll take a tumble. You don’t need to take my word for it. A quick look at my knees, which have become knitted with a patchwork of small scars, tells the story. I can trace some of these marks back years, and have accepted that they will be on my body for life. But what gives? Why don’t our bodies remove old scars? The answer goes to the heart of how our bodies have adapted to protect us. Why do some injuries not cause scarring? “The skin is our protection against the external environment,” says Dr. Corey Maas, an associate clinical professor at the University of California, San Francisco and founder of the Maas Clinic. “It’s a remarkable organ. It’s very important that its integrity be maintained.” The skin consists of three layers. From outermost to innermost, these are the epidermis, dermis, and fat layer or hypodermis. Your skin is a complex organ with three main layers: the epidermis, dermis, and fat layer or hypodermis. Image: Cancer Research UK / CC BY-SA 4.0 After our skin is damaged, a cascade of biological processes fires up. If an injury only damages the epidermis, the wound will typically heal without scarring. But if the injury goes deeper, a scar will form. All scars, big or small, are “designed to repair the skin and restore to you all the continuity and the protective mechanisms that the skin exhibits for the entire body,” says Maas. In other words, our body’s priority is to get the skin strong enough to repel invading microbes—not make it look pristine. How do scars form? There are several stages involved in scar formation. The body first forms a blood clot to prevent bleeding, which then dries into a scab. The immune system then sends specialized cells into the clot to beat back any microbes that may have snuck their way in through the wound. To do so, these cells release specific chemicals (called cytokines), which help prevent infection and send out a loudspeaker message to the body that it’s time for a cleanup in the skin aisle. In response, more specialized cells in the skin called fibroblasts kick into action. These cells start releasing a type of biological scaffolding, known as the extracellular matrix, made up of molecules like long, fibrous proteins such as collagen. These tough proteins increase the scar tissue’s strength. While a wound might close quickly, the full process of restoring the skin’s layers can take months or even years. Related 'Ask Us Anything' Stories Why do your joints hurt when it’s cold? We asked a doctor. Why some people get motion sickness—and others don’t What’s a brain freeze and why do they happen? Is cracking your knuckles really bad for them? Why do we even have baby teeth? Why we have two nostrils instead of one big hole Can you…

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