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The Koebner phenomenon is a medical term used to describe a specific type of skin reaction among those with psoriasis or other skin disorders. This phenomenon is characterized by the development of new psoriasis lesions at the site of a minor skin injury such as a scrape or insect bite. Some of the most common triggers for the appearance of the Koebner phenomenon include poison ivy, eczema, and minor abrasions. The lesions caused by this phenomenon usually disappear on their own over a period of time, although medical intervention may sometimes be needed, especially if a secondary infection occurs. In an attempt to minimize the occurrence of this symptom, patients are often advised to avoid situations that would cause friction or pressure on the skin and to keep the skin moisturized.
In clinical terms, the Koebner phenomenon is considered to be an isomorphic skin reaction. This means that the lesions that develop following injury to the skin mimic those of the underlying skin disorder. Examples of skin diseases that may result in the development of this phenomenon include eczema, psoriasis, and allergic dermatitis. Other disorders, such as lichens planus, vitiligo, and Kaposi sarcoma, may also be associated with this symptom. Outbreaks related to this phenomenon occur directly over the injured area of skin.
Any damage to the skin can result in the Koebner phenomenon for those who are susceptible. Insect bites, vaccinations, and tattoos can all cause new skin lesions to form. Something as simple as clothing or a seat belt rubbing against the skin may cause this type of reaction as well. The new lesions do not usually appear immediately following the injury. Instead, they tend to develop several days or weeks after the skin has been damaged. Treatment is not always needed, although topical medications designed to treat the underlying skin condition may speed up the healing process.
Prevention is usually suggested as the best way to manage the Koebner phenomenon, although this is not always possible. Proper medical treatment of the original disorder is important, as the new lesions are more likely to develop during an outbreak. Insect bites and sores should not be scratched, as this increases the chances of skin injury. Sunburn, scrapes, and other forms of skin trauma should be avoided whenever possible and treated immediately if they do develop. Individualized questions or concerns about the Koebner phenomenon should be discussed with a doctor or other medical professional.