Koebner Phenomenon: When Skin Irritations Trigger Psoriasis Plaques

Cuts, scrapes, bug bites, and sunburns are certainly annoying. But if you have psoriasis, they’re more than just a source of irritation — they’re a potential trigger for a psoriasis flare. And it all boils down to the Koebner phenomenon, a reaction that causes new psoriasis plaques to form wherever you experience a skin infection or injury.

Whether it’s under a controlled situation like surgery or in the event of an accidental scraped knee, people susceptible to the Koebner phenomenon risk getting a new spot of psoriasis, says Christopher Morris, MD, a rheumatologist with Arthritis Associates in Kingsport, Tenn.

German dermatologist Heinrich Koebner first described the event in 1876 (hence the name). Psoriasis plaques due to the Koebner phenomenon are believed to affect up to half of people with psoriasis, and some people will develop a new lesion every time their skin is injured.

What Triggers the Koebner Phenomenon?

Documented triggers of the Koebner phenomenon include:

  • Bruises
  • Cuts and scrapes
  • Bug bites
  • Poison ivy or poison oak
  • Sunburns
  • Burns caused by fire or chemicals
  • Friction burns
  • Rashes caused by allergies or irritants
  • Surgical incisions
  • Tattoos
  • Skin diseases like eczema and folliculitis

Even everyday activities like thumb sucking, shaving, coloring your hair, manicuring your nails, or wearing poorly fitted shoes can cause enough skin irritation or injury to prompt the Koebner phenomenon.

Any section of the skin can be affected by the Koebner phenomenon, even areas that usually aren’t affected by psoriasis, such as the face. You might even miss the association between a scratch or scrape and a psoriasis flare, as it usually takes between 10 and 20 days for the new psoriasis plaque to form. However, the flare could happen in as little as three days or as long as 10 years, depending on the individual.

Researchers have identified several factors that can contribute to triggering the Koebner phenomenon, including:

  • The season. Koebner lesions occur more frequently in winter than in summer.
  • The severity of psoriasis.People who are currently experiencing a psoriasis flare or who have had psoriasis for a longer period of time are more likely to experience the Koebner phenomenon.
  • Scar tissue.Places on the body where scars are more likely to form are also more prone to a psoriatic plaque.
  • Stress.Stress has been shown to exacerbate psoriasis, and it is suspected to also make the Koebner phenomenon more likely.

How to Avoid the Koebner Phenomenon

To avoid a Koebner lesion, quickly clean and dress any wound, says Dr. Morris. That way, you're more likely to avoid a skin infection and the accompanying inflammation that could trigger a flare.

Because Koebner lesions are more likely to form when your psoriasis is active, take particular care to avoid any skin injury during a psoriasis flare. "Try not to get scratches, scrapes, or cuts where you have active psoriasis because that only makes the phenomenon worse," Morris suggests.

Protect yourself by wearing long sleeves and pants outdoors. This will help you avoid sunburn and prevent scrapes or scratches caused by brush and thorns.

If you do get a cut or bug bite, for example, be sure to leave the scab alone as it heals. The National Psoriasis Foundation warns that picking will only increase the chance of developing a Koebner psoriasis plaque.

Finally, contact your doctor if you see any signs of skin infection such as redness, swelling, or warmth at the injury site.

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