Heinrich Koebner first described physical trauma as atrigger and exacerbating factor for psoriasis in 1872. 35He observed the development of psoriatic lesions after adirect cutaneous injury, such as excoriation, tattoos, burns,and animal or insect bites, in previously normal-appearingskin (Figure 1, “Flare”). The new psoriatic lesion wascharacterized morphologically as identical to the injury site,known as an isomorphic response. The Koebner response hasbeen observed with other dermal diseases such as vitiligoand lichen planus, but the frequency for its manifestation ishigher among psoriasis patients. The prevalence of Koebnerresponse in psoriasis patients ranges from 24%–51%. 36Psoriasis onset following an injury may take anywherefrom 3 days to 2 years to develop, and may be dependenton seasonal variation (more frequently in winter) as well asdisease severity (pre-existing and stability of psoriasis).