National Psoriasis Foundation


Koebner Phenomenon

The skinned knees, garden scrapes and bug bites of summer are annoying to everyone.

In people with psoriasis, these minor skin traumas can also trigger what's called the Koebner phenomenon—psoriasis plaques that form at the site of a skin injury.

New lesions develop where the skin is injured

The Koebner phenomenon is named after Dr. Heinrich Koebner, a German dermatologist who noticed the phenomenon in the 19th century.

A slight scratch won't cause koebnerization, but a cut or bite that damages the dermis (the layer of skin below the surface) may begin to show lesions.

As many as 50% of people with psoriasis experience the Koebner phenomenon, and some people develop a new psoriatic lesion each time the skin is injured.

Common triggers of the Koebner phenomenon:

Some common summertime triggers of Koebner phenomenon are:

  • Bug Bites
  • Bruises and scrapes
  • Poison ivy or poison oak
  • Burns, including chemical burns and sunburn

The phenomenon can also be caused by constant pressure and rubbing, medical processes such as injections or vaccinations; skin blemishes from acne, herpes or chickenpox; or from acupuncture or tattoo needles.

Koebner usually occurs within one to two weeks of injury to the dermis but can appear as early as three days or as late as three weeks from the trauma.

Tips to avoid Koebner

  • Lesions from koebnerization are more likely to form when you already have active psoriasis plaques, so be particularly careful during a flare.
  • Wear long sleeves and pants when hiking or gardening in brushy, thorny areas to avoid scrapes as well as poison ivy or poison oak.
  • Avoid sunburn.
  • If you do get an injury, treat it quickly to avoid inflammation or infection that could increase the chances of koebnerization.
  • Don't pick or scratch at scabs or bug bites.

Additional reading:

Learn more about the causes of koebnerization, and how the phenomenon was discovered:

National Psoriasis Foundation Our Mission: To drive efforts to cure psoriatic disease and improve the lives of those affected.