If you’ve got psoriasis, you may have experienced something known as the Koebner phenomenon, in which lesions form at the site of a skin injury, such as a cut or burn.
Statistics suggest that 25 to 30 percent of people with psoriasis are prone to the Koebner phenomenon; it can also occur with other skin conditions, including vitiligo, lichen planus, and viral warts. The Koebner phenomenon is believed to affect between 21 and 62 percent of those with vitiligo.
Here, we’ll look at the types and symptoms of the Koebner phenomenon, what causes it, how it’s treated, and what you can do to prevent it.
Named after 19th-century German dermatologist Heinrich Koebner, the Koebner phenomenon causes lesions in people with psoriasis, vitiligo, or lichen planus following a skin trauma or inflammation. The lesions resemble those associated with the person’s existing skin condition. The scientific name for these skin changes is isomorphic lesions, meaning lesions in a new location.
Reactions related to or resembling Koebnerization include:
Pseudo-Koebner Phenomenon A virus, bacteria, or fungus causes an infectious reaction that can resemble Koebnerization.
Reverse Koebnerization Existing lesions disappear following a skin trauma in the same area.
Pathergy Papules, pustules, and ulcers appear at the site of a trauma in people with other conditions, such as Behcet’s disease.
Wolf’s Isotopic Response New lesions appear after a trauma in people with no history of psoriasis or other Koebner-related skin conditions.
Occasional Lesions Koebnerization sometimes affects an individual after a skin trauma, but not always.
If you have psoriasis, lesions will appear on the area of skin that was injured. The lesions often run in a line.
People with psoriasis and other skin conditions are either predisposed to the Koebner phenomenon or they aren’t. The skin’s reaction to an injury is classified as:
None
Abortive (lesions vanish spontaneously after approximately two weeks)
Minimal (lesions appear around the area of trauma)
Maximal (widespread lesions)
If you usually have plaque psoriasis and are prone to the Koebner phenomenon, you may notice new lesions at the site of the trauma that are:
Raised
Discolored
Scaly
Itchy or painful
Psoriasis-related Koebner lesions usually appear 10 to 14 days after a skin trauma. In some cases, however, they can appear in as few as three days; in others, it can take up to two years after an injury for them to form.
How long symptoms take to appear likely depends on:
The type and location of the injury
Its width and depth
Other individual factors, such as a person’s overall health
Koebnerization can appear at different stages of psoriasis. Some people have psoriasis for many years without experiencing this phenomenon but become prone to it, or “Koebner-positive,” later in life.
Experts don’t know exactly why Koebnerization happens or why it affects some people and not others.
Because it seems to occur with autoimmune diseases, such as psoriasis, it may be an immune-mediated response. The process may involve changes in cytokines (proteins that control inflammation), T-cells, skin cell growth, or other actions. More research is needed to identify the precise cause.
Injuries that can trigger the Koebner phenomenon include:
There’s no specific test used to diagnose the Koebner phenomenon.
To determine if new lesions are linked to an existing skin condition, your doctor will ask about your symptoms, history of psoriasis or other skin conditions, and if you’ve experienced any skin trauma recently.
They may also take a skin sample to look for signs of psoriasis under a microscope.
There’s no specific treatment for lesions caused by the Koebner phenomenon. Instead, your doctor will likely recommend treating it as you usually treat a typical psoriasis skin flare.
For psoriasis symptoms, options may include:
Topical creams and ointments
Light therapy
Oral or injected medications, such as biologics, for more severe disease
Complementary therapies, such as fish oil supplements or aloe vera cream
Home and lifestyle remedies, such as moisturizing and avoiding scratching
In addition to staying on top of your regular psoriasis treatment plan, you can minimize your risk of the Koebner phenomenon by taking these measures to avoid skin trauma:
Use a natural insect repellent to avoid bites. Note that repellents with DEET may cause a skin reaction if you have psoriasis.
Wear protective clothing when doing outdoor activities such as gardening or hiking.
Take measures to avoid scratching.
Your doctor can advise you on sun safety and the best cosmetics, sunscreens, insect repellants, moisturizers, and other skincare products. If you require a surgical procedure, make sure your surgeon knows that you are prone to the Koebner phenomenon. Take the same precaution before getting a tattoo or piercing. Many people with psoriasis have tattoos, but it’s worth checking out the pros and cons before getting one.
These home remedies and other strategies may help you manage psoriasis and skin flares, whether or not they result from the Koebner phenomenon:
Bathe daily in lukewarm water. Try soaking for 15 minutes in a bath with baby oil, Epsom salts, or oatmeal.
Use mild and fragrance-free skin products. Ask your doctor or pharmacist for recommendations.
Keep your skin moist. Use creams, lotions, oils, or ointments, depending on your skin type, and apply them immediately after a bath. Use a humidifier in dry weather.
Cover lesions overnight. Apply a moisturizer at bedtime and wrap plastic around the skin. Remove and wash in the morning.
Stay safe in the sun. Ask your doctor if exposing skin lesions to the sun is safe and which sunscreens are best for you.
Keep cool. Wear light clothing, use air conditioning if you can, and apply cool packs wrapped in towels to affected skin.
Maintain a healthy lifestyle. This includes maintaining a moderate weight, managing stress, exercising regularly, and following a varied and nutritious diet.
There are no complications specific to the Koebner phenomenon. Complications are the same as with any psoriasis flare, including a secondary infection.
In a study published in 2019, experts compared the appearance of the Koebner phenomenon in two people with lichen planus: one with light skin and one with dark skin. Despite having the same diagnosis, the lesions looked different on the two skin colors. The authors of the study emphasize the need for greater awareness of how Koebnerization can look on different skin tones.
The National Psoriasis Foundation notes that Americans with darker skin have to wait longer for a diagnosis and are more likely to experience severe psoriasis than white Americans.
One reason is that medical descriptions of psoriasis often describe features as seen on light skin. Even when people with darker skin can access the medical help they need, their doctor may not recognize the signs of psoriasis or the Koebner phenomenon.
The Koebner phenomenon, or Koebnerization, refers to symptoms of psoriasis or other skin conditions that appear following a scratch or other skin trauma.
Koebnerization can occur with various conditions but commonly affects people with psoriasis, vitiligo, lichen planus, or viral warts.
If you have psoriasis, you can lower your risk of Koebnerization by following your treatment plan and taking measures to minimize skin injuries.
