The appearance of a skin lesion as a result of nonspecific trauma (e.g., sunlight, burn, operative wound). It will appear at the trauma site and may be of a type found elsewhere on the skin. It may be seen in lichen planus or eczema but is particularly characteristic of psoriasis. The lesion must be sufficient to act on the papillary and epidermal layers of the skin and will appear in 3 to 18 days following the trauma.
In individuals with skin conditions like psoriasis and lichen planus, new lesions can form, often as a result of scratching.