Can someone use air freshener on Shabbos after bathroom use?
Most permit the use of air freshener on shabbos.
According to the Bavli, the labor of Zoreh is defined as sorting the undesirable from desirable via the force of air. According to the Jerualem Talmud, however, the melachah is defined as dispersal via the force of air. The Rema (end of 319) maintains that the definition according to the Jerusalem Talmud should be used, and accordingly prohibits spitting into the air. Some have prohibited the use of sprays, which disperse into the air, based on this definition.
However, the dispersal force of common deoderants and air fresheners isn’t from the air, but rather from the propellent within the can, and other authorities are therefore lenient in their use. Moreover, the ruling of Rema is contested by other authorities, who (based on the definition of the Bavli) are not stringent concerning spitting into the air, and similar activities.
A second issue that needs to be explained is the matter of producing a scent on Shabbos. Although Rema rules that it is forbidden to produce a scent on Shabbos–a ruling that most rishonim do not concur with–poskim explain that this refers specifically to creating a scent upon clothing. Therefore, the prohibition does not apply to air freshener, and it is permitted to make use of it on Shabbos.
Sources: Rema, Orach Chaim 319:7; Chayei Adam 15:1 (disputes ruling of Rema); Cheishev Ha’Efod 3:15 (prohibiting spray, out of concerning for zoreh); Minchas Yitzchak 6:26 (permitting); Rema, Orach Chaim 511:4 (concerning creating a scent on Yom Tov); Eliyah Rabba, She’elas Yaavatz 41, Chacham Tzvi 92 (limiting the stringency).