Flagellate dermatitis (FD) exhibits a striking clinical appearance similar to whiplash marks. General dermatologists are likely to encounter this clinical appearance as a more localized presentation of phytophotodermatosis. Jellyfish stings may also cause localized linear or FD. Chemotherapeutic agents such as bleomycin, doxorubicin, docetaxel, and trastuzumab are well-recognized causes of a widespread FD and it may more rarely be seen in connective tissue disease such as dermatomyositis or Still disease. In our case, this was a presentation of shiitake mushroom dermatitis.