User Avatar KopaFeb 23, 2021

Why Psoriasis Tends to Appear on Scars

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.”

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