Résumé dans la langue de publication, traduction non disponible An acridone derivative represented by the following formula (I) and a pharmacologically acceptable salt thereof are effective in preventing and curing diseases which are associable with histamine, leucotriene, etc. and in preventing and curing allergic diseases such as asthma, allergic rhinitis, atopic dermatitis, urticaria, valerian fever, digestive tract allergy, or food allergy. wherein R**1 - R**8 severally represent a hydrogen atom, a lower alkyl group, etc. and n represents an integer of 1 - 6.