When skin lesions, or sores, form where an individual doesn’t typically have them, this is known as the Koebner phenomenon. It can happen to people who have conditions like psoriasis and to people who have no other conditions.

The Koebner phenomenon describes the formation of skin lesions on parts of the body where a person doesn’t typically experience lesions. This is also known as an isomorphic response.

It’s long been associated with skin conditions such as psoriasis and vitiligo. However, more recent research confirms that it can also occur in people with no preexisting skin conditions.

The Koebner phenomenon is named after the dermatologist Heinrich Koebner, who was the first to observe this condition in the 19th century.

Koebner noted that some people with psoriasis developed lesions in areas in which the skin had been traumatized. This could be from a cut, bruise, or burn.

Lesions may also develop on parts of the body where the skin is irritated by a waistband, belt buckle, or bra strap. In all of these cases, the lesions appeared in areas outside of the usual spots affected by psoriasis.

Psoriasis can appear anywhere on the body, but it usually affects the:

  • scalp
  • knees
  • elbows
  • lower back

The Koebner phenomenon is an aspect of psoriasis that’s well-known but not completely understood.

Researchers aren’t exactly sure what causes it. Theories suggest that it’s spurred on by the presence or increased production of certain proteins and substances, some of which are inflammatory. They include:

  • tryptase
  • interleukins IL-6, IL-8, IL-17, and IL-36y
  • stress proteins
  • nerve growth factor
  • vascular endothelial growth factor
  • auto-antigens

According to a 2019 study, the Koebner phenomenon affects around 25 to 30 percent of people with psoriasis. Triggers include:

Scientists have also identified a condition in which superficial skin injuries or trauma trigger more profound responses than lesions. In some cases, skin damage can lead to psoriatic arthritis (PsA).

Unlike osteoarthritis, which results from wear and tear on the joints, PsA is an autoimmune disease. In people with psoriasis, an overactive immune system attacks healthy tissue in the joints. This can result in pain, stiffness, and inflammation in the affected joint.

The development of PsA following surface injury is sometimes referred to as deep Koebner phenomenon.

The symptoms of the Koebner phenomenon are treated in the same way that psoriasis and PsA are treated. If you experience symptoms, you should consult a dermatologist who specializes in treating psoriasis.

For skin lesions, they may recommend topical medications, ultraviolet light therapy, or oral medications.

PsA is usually treated with a combination of medications. Mild cases may only require nonsteroidal anti-inflammatory drugs (NSAIDs). If you have a more serious case, you might need drugs that suppress the immune system.

Your dermatologist could suggest steroid injections be made directly into the affected joint, which will reduce inflammation and other symptoms. If the damage has been too great, you may need a joint replacement.

If you notice scaly patches of skin, have them diagnosed by a dermatologist. There are several conditions that leave dry patches of skin, such as eczema and seborrheic dermatitis. Getting a confirmed diagnosis will help make sure you get the best treatment.

If you already know you have psoriasis, talk with your dermatologist about the Koebner phenomenon and what you can do to help minimize your odds of experiencing it. The advice may be as simple as treating your existing psoriasis to the best of your ability and protecting your skin in every way possible.

Be sure to pay attention to skin that comes in contact with your waistband or bra or other clothing that might irritate it. The earlier you can spot the symptoms, the earlier it can be treated, and the sooner you can find relief.

There’s no way to predict who will develop this condition, but having psoriasis is a key risk factor. In general, people with psoriasis are advised to take greater care of their skin than the general public. Taking care of your skin means following the advice below:

  • Protect your skin from sunburn, and keep your skin moist.
  • Use a moisturizer and a humidifier if you live in an area with especially low humidity.
  • Try to avoid bruising or cutting your skin.
  • Keep your scalp clean, and use tar shampoos if your doctor recommends them.
  • Leave lesions alone unless you’re applying a topical medication. Don’t pick or scratch lesions, as this can make flare-ups worse.