You don’t have to share, hopefully it was recent and we’ll leave it at that.
The reason I bring it up is I just got back from camping in the deep woods. This isn’t camping at a camp site, this is camping with no electricity, no running water (‘cept in that muddy creek). There is no road to where we camped, so we had to carry everything that we ate or drank in and back out with us. We were out there for four days. The only thing that saved us is that we smelled more of campfire smoke than anything else.
This wasn’t the most hard core camping I’ve ever done but it did make me think about what it’s like to go without a shower for a few days. It’s made me realize that PCs, at least in the games we run, would be going without for days on end and seriously, they’d want a shower bad. If you’re not running a modern campaign players may be used to going for months without a shower or bath but if we had a large enough body of water to jump in, we would have done it. This isn’t a huge revelation, I think you probably know you want a shower after a day or so.
So what can you do with that? Normally here I’m suggesting a mechanic. Unless I was trying to tempt the PCs into showering in some sacred springs, I don’t think there’s a way to quantify the feeling of funk. It’s not going to kill you. Maybe it would make you more likely to catch a disease but that’s debatable, we actually shower too often for our skin to be healthy. It could lower the character’s charisma because they stink but that’s not a huge deal.
What I’d suggest here is to just role play it. Especially if the characters are used to a civilized environment. Every once in a while, mentioning that it’s getting really hard to stay clean. That their fingernails have dirt under them no matter how often they clean them. It’s weird, but there’s a very low level panic that you start to get when you haven’t showered. I wondered if it’s safe to touch my food with my hands even though I’d cleaned them with disinfectant. I think that’s best simulated by mentioning little things that suggest it’s time to bathe to the characters. They’ll start to wonder if you’re going to hit them with a disease or make it really count in the game somehow. Some players are just plain unnerved by being told their characters smell. Some will laugh off the first round of mentioning the smell. Saying it twice won’t really make any more of an impact though. It has to be something different each time to really get the players bothered by it. Like their skin is feeling really oily after sweating all day. I could keep going but it’s just not pleasant reading but that’s the point. You want the players to imagine feeling nasty.
So why would you go through this? For one, it’s real, so as a simulation the game feels more real. More importantly, it will engage more of the player’s senses and that gets them imagining the world around them, make it more vivid. Engaging the sense of touch makes a situation more memorable and smell has the strongest connection to emotion and memory of any sense. This is just one tactic to bring out those senses and involve them in your games.