Mast cell degranulation inhibitors having a carboxyl group have not been developed as external preparations due to the low transdermal permeability thereof. By formulating external preparations thereof, side effects on the internal organs by oral administration can be avoided. Some of the mast cell degranulation inhibitors show drastically inferior photostability, which is also one cause of suppressed development of the drug as an external preparation. The present invention aims at improving the transdermal permeability and photostability of mast cell degranulation inhibitors by forming a salt of the mast cell degranulation inhibitor with an organic amine. Consequently, an external preparation of a mast cell degranulation inhibitor can be provided and the photostability of the mast cell degranulation inhibitor itself, and a preparation containing same can be improved.