a curing agent for fat necrosis which contains a dithia derivative represented by the general formula ## str1 ## wherein r and r 1 may be either the same or different and denote a lower alkyl group ; n denotes an integer of 0 , 1 or 2 ; and a denotes -- ch 2 --, ## str2 ## m being h or a salt - forming rest , -- ch ═ ch --, -- ch 2 ch 2 --, or ## str3 ## and a method for curing said disease using the said curing agent .