It is an object of the present invention to provide an external preparation having enhanced transdermal penetration of a mast cell degranulation inhibitor. It is also an object of the present invention to provide a method for improving the photostability of a preparation containing a mast cell degranulation inhibitor. The present invention provides an external preparation containing a mast cell degranulation inhibitor and a topical anesthetic. Further, the method for enhancing the photostability of a preparation containing a mast cell degranulation inhibitor according to the present invention includes adding a topical anesthetic thereto.