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Do your scratches, sunburns, insect bites, or tattoos become scaly patches after they’ve healed? For some people with psoriasis, skin injury can cause psoriasis symptoms in the affected area. This is known as the Koebner phenomenon, and it occurs in about 25 percent of people with psoriasis. It also induces multiple types of psoriasis.
“I get psoriasis wherever I cut myself,” reported one MyPsoriasisTeam member. “Ingrown hair, scrapes, or pimples all become new plaque psoriasis spots on me,” shared another.
The Koebner phenomenon is the appearance of new psoriasis lesions on previously unaffected areas of skin. A psoriasis flare will develop where the skin has been injured, whether through a scratch, burn, tattoo, or bug bite. The Koebner phenomenon is often referred to as Koebnerizing or Koebnerization.
“Once the skin heals, a new patch [of psoriasis] will usually arrive in its place,” explained one member.
Flare-ups can occur in areas not typically prone to common triggers, some members say: “My psoriasis appears in some unusual places, all of which are areas of repeated pressure. I also get rashes where my lip and nose are pierced.” “Tongue, too,” shared one member.
Other forms of skin irritation can lead to Koebner flare-ups as well. For example, there have been at least two recent case reports that document the Koebner phenomenon being triggered near the ears by wearing face masks during the COVID-19 pandemic. And one member experienced Koebnerization from hair removal. “My mistake was waxing — psoriasis pops up anywhere the skin has been injured. I should have known better. Now I'm stuck with awful-looking legs.”
It is well known that psoriasis is caused in part by a misfiring of the immune system, and both immune cells and skin cells can factor into the formation of psoriatic lesions. It is not fully understood why flare-ups happen after an injury, however.
During the past several years, a great deal of research has expanded our knowledge of psoriasis and the Koebner phenomenon, with much of this research focusing on molecules involved in inflammation, including molecules called IL-17, IL-6, and CCL20.
IL-17 (IL stands for interleukin) is known to be one of the key molecules that drives psoriasis. IL‐17 starts the process of wound repair that leads to the build-up of excess skin layers in psoriasis. Medications that inhibit IL-17 — such as the biologics Cosentyx (secukinumab) and Taltz (ixekizumab) — have been authorized by the United States Food and Drug Administration (FDA) to treat moderate to severe psoriasis.
A protein similar to IL-17, called IL-6, has long been associated with psoriasis. One study looking at IL-6 and the Koebner phenomenon showed an increase of IL-6 in skin cells from people who had a Koebner response compared to those who had no response. Actemra (tocilizumab) is an IL-6 inhibitor approved by the FDA for the treatment of rheumatoid arthritis, and it has also been reported to improve symptoms of palmoplantar pustular psoriasis and psoriatic arthritis.
Another important molecule thought to be responsible for the Koebner phenomenon is CCL20, which is a signaling protein. It recruits a special type of immune cell called a T cell. One study shows that damaged skin cells make more CCL20. Researchers have recently discovered the molecules that help turn on CCL20 in skin cells.
These are just a few of the studies that have been done to determine how molecules of the autoimmune response cause the Koebner phenomenon. Studies like these are exciting because they provide the basis for expanding treatments.
Koebner lesions from scratches and other skin injuries are treated the same as regular psoriasis plaques. Treatments include:
Because Koebnerized skin can crack, bleed, and lead to infection, it’s important to treat the area as soon as possible. Read more about treatments for psoriasis.
Here are some tips for preventing or managing skin injuries and lesions:
Consult your doctor for medical advice before starting any new treatment.
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Are your psoriasis flares sensitive to scratches on your skin? Share your experience in the comments below, or start a conversation by posting on MyPsoriasisTeam.