Cuts, scrapes, and minor burns can be annoying when you have healthy skin. But if you have psoriasis, these injuries are more than a source of aggravation — they can trigger a psoriasis flare.

This problem is known as the Koebner phenomenon, and it affects about 1 in 4 people with plaque psoriasis, says the National Psoriasis Foundation (NPF).

Named after 19th-century German dermatologist Heinrich Koebner, the Koebner phenomenon (also called Koebnerization) describes a psoriatic rash that occurs at the site of an injury or irritation.

People susceptible to the Koebner phenomenon risk getting a new patch of psoriasis in areas where they don’t typically experience lesions, explains Teo Soleymani, MD, a dermatologist at UCLA Health.

“The new lesion could be near an existing plaque, or it could be in a distant location,” explains Dr. Soleymani. “Once the Koebner phenomenon occurs, the new location can end up becoming a chronic source of flares.”

The exact physiological mechanism involved in the Koebner phenomenon isn’t fully understood, but research suggests that the immune system plays a role.

“In people with chronic plaque psoriasis, the immune system in the skin is a little overactive,” Soleymani explains. “It may be that once the immune system gets ‘turned on’ to heal the injured or irritated skin, it doesn’t know when to turn off, and as a result you get the development of psoriasis.”

What Does the Koebner Phenomenon Look Like?

Koebner lesions tend to have the same features as a person’s existing psoriasis plaques. The new lesions can be raised, discolored, scaly, itchy, and painful. They can also crack and bleed.

These new psoriatic lesions also tend to follow the lines or shape of the injury itself, Soleymani notes. “Psoriasis can be itchy, and you can often see clear linear streaks of psoriasis plaques develop where the nails frequently scratch,” he explains.

In many cases, Koebnerization will occur within days of an injury; in other cases, new plaques might not show up until years later. As a result, you might not make the association between a scratch, scrape, or chronic irritation and a new flare.

“How quickly the Koebner phenomenon occurs seems to depend on the degree of irritation or trauma,” Soleymani says. “With a deep scratch, surgical wound, or sunburn, the Koebner phenomenon can occur a few days or a week later. With milder injuries, such as chronic rubbing or irritation, it could be many years before you see new plaques develop.”

What Triggers the Koebner Phenomenon?

New plaques due to Koebnerization can be the result of a minor injury to the skin, such as a cut, scrape, or nick while shaving, or a more significant trauma, such as surgery.

Injuries that are skin deep, meaning they affect the epidermis (the outermost layer of skin) and dermis (the layer of skin just below the surface) tend to be most prone to Koebnerization, according to a review article published in September 2019 in the International Journal of Molecular Sciences.

If you have psoriasis and get a tattoo, which involves having a specialized needle with ink rapidly enter and exit the top layers of your skin, you run a high risk of experiencing the Koebner phenomenon in the tattooed area, says the NPF.

But even a minor irritation, if it’s prolonged, can break the skin’s surface and trigger a Koebner response. Wearing a tightly fitted face mask due to the COVID-19 pandemic, for example, can be enough to cause a problem.

A study published in February 2021 in Dermatologic Therapy found that some people with psoriasis develop Koebnerization in areas that come into contact with masks, such as the cheeks, mouth, and nose, and the skin around the ears.

Other triggers of the Koebner phenomenon include:

Sunburns
Burns caused by hot objects, fire, radiation, or chemicals
Friction burns
Bug bites
Piercings
Razor burns
Vaccinations

How Is the Koebner Phenomenon Treated?

If you experience any new areas of psoriasis, you should check in with your dermatologist as soon as possible, advises Soleymani. Your physician can determine if the problem is Koebnerization or something else entirely, such as an allergic reaction or infection.

“If it is the Koebner phenomenon, early treatment is important because it can help dial down the immune activity and keep the new plaque from becoming chronic,” Soleymani adds.

Dermatologists treat psoriasis flares due to the Koebner phenomenon the same way they treat other psoriasis symptoms. They may recommend:

Topical Therapy These ointments and creams include steroids, synthetic vitamin D, retinoids, and salicylic acid.
Phototherapy This form of treatment involves exposing the skin to ultraviolet light on a regular basis and under medical supervision. Phototherapy can be done in a doctor’s office, outpatient clinic, or at home with a phototherapy unit.
Oral or Injected Medications These include steroids, biologics, and targeted immunotherapies.

How Can You Avoid the Koebner Phenomenon?

To reduce your risk of unexpected plaques, try not to irritate your skin, and do your best to avoid injuries. Here are nine strategies that can help.

Follow your psoriasis treatment plan. This can help you avoid flares — and fewer flares means less itchiness and less scratching.
Protect your skin from the sun. To avoid burning, use a sunscreen that contains zinc oxide or titanium dioxide and has an SPF of at least 30, advises the NPF.
Wear long sleeves and pants for outdoor activities whenever possible. This will help you avoid sunburn and prevent scrapes or scratches caused by brush and thorns.
If you need to have surgery, talk to your dermatologist beforehand. “Sometimes we treat the scar right away with topical steroids and things that will help the anticipated Koebnerization and head off a problem,” Soleymani says.
Clean and bandage any wounds right away. This helps avoid a skin infection and the accompanying inflammation that could trigger a flare.
Take precautions if you opt to get a tattoo. Let the tattoo artist know about your condition, and avoid tattooing areas that are prone to flares, advises the NPF. Afterward, keep the treated area clean to avoid infections and hasten healing.
Use a face mask extender. These adjustable elastic straps, which run across the back of your head, can prevent chafing and irritation behind your ears.
Shave carefully — or avoid it altogether. If you get psoriasis on your legs, talk to your doctor about whether waxing, electrolysis, or laser hair removal might be a better option for you.
Avoid getting vaccines on or near plaques. These jabs aren’t as likely to induce Koebnerization as other skin injuries, says Soleymani, but you can reduce the risk by steering clear of any active psoriasis plaques.