Yuck. Mass washing.
Maybe buy disposable undies? Two packs -most have six units- just to be safe. BTW, they sell them both bikini and boxer shorts styles. Any Watson, Cosmed, local supermarket or pharmacy should have them.
Oh, they also sell disposable socks. Better safe than sorry.
Which reminds me: the langbais, the ubiquitous whiote and blue sandals, definetively get a pair.