Sir, We have observed that Balaustium murorum (Acarina: Erythraeidae) can cause dermatitis. B. murorum has a habit of climbing walls and invading buildings, and has very generalized feeding habits. Its biology is not yet fully known, however, and more attention needs to be given to infestation on buildings, walls and weeds around hospitals during summer. In this paper, we report a case of extensive dermatitis caused by B. murorum. CASE REPORT AND DISCUSSION