I could mean a couple of things. The first and most important, does he work outdoors and sweat alot? If so, his private area suffers, and he feels he needs to wash after work, as it may be all sweaty. Secondly, it could be that he's cheated, but you should not jump into conclusions without first talking things out, ask him why he does that? Also, notice any changes in his behavior, when a man strays they tend to be dubius about what they have been doing, and usually they trip up on their own excuses. Honestly without knowing him personally I can't really say what's going on. But it does sound like he sweats alot, if he's doing it every day. I mean, stop and think could he be cheating on you every day?
Good Luck