For some living with psoriasis, a harmless cut or graze can sometimes develop into a full-blown flare-up, due to something called Koebner's phenomenon

Most of us have been there. We’re looking down at our cell phone as we walk, bump into a [insert hard and sharp object of your choosing], and scrape our skin. And, for many people, that’s where the story ends. For others, maybe it ends with a bandage and some ice too! But for around 25% of people with psoriasis, the story is far from over. For these people, a seemingly harmless cut or graze can sometimes develop into a full-blown flare-up.1

Say what?!?!

We know, it sounds hard to believe, right? But the connection between skin injuries and flare-ups dates all the way back to 1876, when a German dermatologist named Heinrich Koebner discovered that new lesions in people with psoriasis often occurred on sites of previous skin injury.2 These were typically characterized by distinct lines that followed scars from cuts and scrapes or surgical incisions. It was this observation that gave rise to what scientists now refer to as Koebner’s phenomenon.

The tell-tale signs of a Koebner’s response

You may have experienced a Koebner’s response yourself without even realizing. There’s typically a delay of around 10-14 days before a psoriasis plaque forms following skin trauma; and, in some cases, delays can even be several years!3 Yes, you read that correctly - a cut or scrape from several years past could in fact lead to a psoriasis flare-up!

Most Koebner’s responses look like neat, linear plaques that extend directly from the site of a previous cut or scrape. But that’s now always the case. Some people can experience less distinct patches following more subtle types of skin trauma such as sunburn or a rash. And in some people, new plaques can even be triggered by the slightest things including insect bites, bruises, shaving nicks and blisters.

What causes Koebner’s phenomenon?

As if this whole concept isn’t frustrating enough, what’s possibly even more frustrating is that scientists don’t really know what’s behind Koebner’s phenomenon. Research suggests it may be due to changes in the blood capillaries supplying the skin, which somehow trigger inflammation, but the exact mechanism is still a mystery.

We do know however, that Koebner responses typically happen more in winter; and people who are already having a flare up are more likely to experience them – particularly those with severe psoriasis.3

Ways to reduce your risk of a Koebner’s response

Short of shrouding yourself in bubble wrap and never leaving the house again, there’s not a great deal you can do to avoid skin injuries completely. There are common sense ways to help minimize your risk. For example, cover your arms and legs during activities that might involve skin contact, like gardening or sports. Also, make sure your clothes and shoes fit properly, to prevent rubbing. And, if you know that you are someone who reacts to every cut and graze, it makes sense to avoid unnecessary skin traumas like acupuncture and tattooing.

And here’s an important one: if you need surgery of any kind, and you know your skin reacts badly to injury, it’s important to mention this to your surgeon as it could potentially affect wound healing.

Remember, Koebner was a dermatologist!

The very man for which Koebner’s was named after was a dermatologist – he was trained to identify this type of flare-up. If you’re experiencing unusual flare-ups, don’t play doctor and just assume that Koebner’s is the culprit. You should always talk to your dermatologist/doctor about changes in your psoriasis and get their advice on the best ways to manage them.

And in the meantime, we could all probably spend a bit less time looking down at our smartphones and watching where we’re going to avoid the unnecessary war wounds of texting!


1. Developing Shingles-Induced Koebner Phenomenon in a Patient With Psoriasis: A Case Report. Zhao YK, Zhang YQ, Wang F, Wu HH, Luo ZY, Luo DQ, Chen WN. Medicine (Baltimore). 2015 Jul;94(26):e1009.

2. The Koebner phenomenon. Sagi L, Trau H. Clin Dermatol. 2011 Mar-Apr;29(2):2316.

3. The isomorphic phenomenon of Koebner. Thappa DM. Indian J Dermatol Venereol Leprol. 2004 May-Jun;70(3):1879.


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