Every year I avoid public transportation here in Israel from Rosh Chodesh Av until 10 Av because the stench of B.O. at times gets so bad it is unbearable.
Some fanatics don't shower during this time other than erev Shabbos if at all until after noon on 10 Av.
Both Rav Ovadia & Rav Moshe Moshe paskened you can & should not only for hygenic reasons but also it is a Chilul Hashem to stink!!!
I myself asked Rav Sholom Marozov one of the mashpiim in Chabad & he said if you can't live with yourself go for it & it is no mitzvah to stink.