woman applying cream to scar on hand

Why Psoriasis Tends to Appear on Scars

By Kerry Weiss
February 23, 2021

You may notice that certain things can trigger your psoriasis—whether it’s stress, your diet, or the weather. But have you ever had psoriasis show up on a scar? If so, you’re not alone. When psoriasis pops up on places where there was trauma to the skin, it’s referred to as the Koebner phenomenon—named after the researcher who first identified this reaction.

“So, if someone gets hit with a baseball on the chest, even if they haven’t had psoriasis there before, a psoriatic plaque may appear shortly thereafter,” explains David Rosmarin, M.D., dermatologist and vice chair of education and research for the department of dermatology at Tufts Medical Center in Boston.

Why Does the Koebner Phenomenon Happen?

Research is ongoing to help identify exactly why this happens, so there’s not a detailed scientific explanation yet. Rosmarin puts it simply: “Psoriasis is fundamentally a disease where the immune system is too active in the skin,” he says. “When there is trauma to an area, that can be activating to the immune system, and that then leads to a psoriatic plaque.”

The Koebner phenomenon occurs in about 25 percent of people with psoriasis. “We can’t predict who will or won’t get it,” says Neil Korman, M.D., Ph.D., the director of the Murdough Family Center for Psoriasis at UH Cleveland Medical Center in Ohio. But if you do get it, you’ll likely get it regularly.”

Are Certain Areas More Susceptible Than Others?

The Koebner phenomenon can appear as a result of any type of skin trauma, including:

  • Scratching the skin
  • Injury
  • Surgical incision scars
  • Vaccinations
  • Sunburn
  • Insect bites
  • Tattoos
  • Stretch marks
  • Alternative therapies such as acupuncture or cupping therapy

Certain areas of your body may be more susceptible to the Koebner phenomenon than others. “One of the theories for why psoriasis is often on the elbows and knees is that those are areas where there may be a bit more trauma—from kneeling down or putting our elbows on things,” adds Rosmarin.

And the new psoriasis plaques might not show up right away. While they typically appear anywhere between 10 to 20 days after the skin trauma, new plaques may not actually show up for years after the skin trauma took place.

How Should I Treat the Psoriasis on My Scars?

When it comes to the Koebner phenomenon, prevention is key. One of the best things you can do, explains Korman, is to avoid doing anything that may injure or scar your skin.

While you should talk to your doctor if you think you’re experiencing the Koebner phenomenon, chances are, your treatment recommendations won’t change. “We don’t do anything special—we treat it in similar ways to how we treat psoriasis elsewhere on the body,” explains Rosmarin.

That may be with topicals, phototherapy, systemic therapies, or biologic treatments. “It depends on the severity of the underlying disease,” says Rosmarin.

Once you’ve established an effective psoriasis treatment regimen, it’s important to stick with it. “Even if you treat psoriasis and it looks better, if you stop taking your medication, it can come back—often in the same location,” adds Rosmarin.

Though if your psoriasis—Koebner phenomenon or not—is affecting your quality of life, it’s important to speak up. “We don’t treat the disease, we treat the patient,” says Rosmarin. “So, if your psoriasis is affecting your quality of life, we can try more aggressive treatments to get it under control.”

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