The Koebner Phenomenon

Why you shouldn’t pick, scratch or rub! 

As I often say, tons of things in dermatology have funny names.  Koebner phenomenon is our dermatology vocabulary phrase today.  It is the phenomenon of things occurring or getting worse in areas of friction or trauma.  Rashes can often occur exclusively in an old scar, avoiding surrounding skin, as seen in the photo.  

The Koebner phenomenon occurs with a number of dermatologic conditions but is most often seen in psoriasis.  Also called the isomorphic response, it is poorly understood, but can be seen in psoriasis, lichen planus, and vitiligo. 

Those with these conditions should
watch for lesions in areas of scars, piercing, tattoos, arthropod bites. 
Consideration should be taken before tattoos in patients with psoriasis.   

Psoriasis is often worse in areas of trauma and friction, including picking, scratching, rubbing, and filing of feet.  This includes elbows and knees for those with plaque psoriasis.  Friction in folds often worsens those prone to inverse psoriasis. To learn more about psoriasis, check out the National Psoriasis Foundation website, and to learn more about inverse psoriasis, check out our post on “What’s this rash in my folds?”

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