Overnight Couple/showering

You don't say anything.
And you don't ASK if they need towels, they should be placed on the guest room bed or dresser.

I wouldn't like it, but I would NEVER say anything. That's just rude, IMO. Like others have said, get a mattress pad if you haven't already. After they leave, just take everything off and let it air out for a day.

You cannot force your guests to shower. You can provide towels and soap but you can't tell them to get in. There are no words needed. If it grosses you out don't invite them over as guests in the future. Or get a heavy duty mattress protector to keep the mattress safe so you don't have to worry about funky guests.

Purchase a mattress protector and keep silent about your guests hygiene practices.

Edit* I would caution you against speaking to them. As a host, your job is to make your guests comfortable, not embarrassed or ashamed. If you are uncomfortable with them staying with you, let them know that you will be unable to host them when they return to your city.

It really is none of your business if they shower to be honest, and if you are concerned about the mattress then get a mattress protector to put under the sheets. If my host implied to me that I was too nasty to sleep in her guest bed I would be highly offended. If you say something be prepared to possibly lose a friend, even if they don't say anything right away, you may just see them limiting contact more and more.

You absolutely can't say anything at all. You can just not invite them again if it's so important to you. I agree about the mattress protector/pad. I also give guests a quick "tour" of their accommodations and tell them where their towels are on a rack in the bathroom, or I put them right on the guest bed. I give them the invitation right when they arrive. You really can't inquire of them after they arrive.

Some people think it's a little icky to use another person's shower, soap, etc. Just as you think it's icky to have BO (and I agree with you). The way to handle that is to put a little basket or display of fresh, individually-sized products like shampoo, deodorant, body wash or soap in a little dish, lotion, etc. I get the travel-size items in the supermarket. It's as big a hint as you are allowed to give and you can only get away with it because it's disguised as a gift!

They were still literally sweating and therefore wet or you all had been sweaty but it dried? If the latter, I wouldn't worry at all about the mattress... I'm very surprised they didn't at least shower the next morning but that night if they just had dried sweat, I don't think there's any lasting impact at all. I had a friend show up once who was a real free spirit. He'd been traveling for I don't know how long and literally smelled like a homeless person. He had to sleep on my couch bc I only had a one bedroom at that point. I was shocked he wasn't going to shower given he finally was in a place with a private shower. Of course I offered!! But he declined. There was no way to completely cover the couch - arm rests etc but even with him, I think bc it was dried sweat, no lasting smell at all. So I think you're over reacting. And how many couples have had long, sweaty sex and fallen asleep before showering?? Their mattresses don't smell...

Egads! I also would be pretty horrified. I would not say anything, but boy I would be sure to air out the room and really clean those sheets. I cannot sleep when I am all sweaty and sticky, not to mention the smell of smoke and gross dirty feet..

Put a water proof mattress pad on the bed.
This is one of the many reasons I love hotels when I visit and when anyone visits me.

One of the reasons I almost always bathe/shower in the evenings is because I like to go to bed CLEAN, so I get why you would be grossed out.
But unless these people are planning to move in with you I wouldn't say anything.
Next time they come just make sure you have a good thick mattress pad/cover on the guest bed, that should be sufficient!

The next time, have the towels beautifully folded on top of the bed and some travel-sized liquid soap bottles on top of the the towels, and as you walk them into their room upon arrival, you can say with a big smile, "I'm sure you had a long trip (long day, whatever) so come on down to have some coffee after you shower and freshen up, and we'll go out to dinner later. Take your time." Whatever applies. Don't ever order them to shower, but mention the idea of "Let's all go get ready to go out" or if it's late, try "I'm off to have a shower after all that walking around, here are your towels too."

They are guests and, I assume, friends? Telling them they're ripe -- unless they are VERY close friends indeed -- is just not good form. If there are future visits, just say you can't manage to have them at your house but will give them numbers for a few close hotels.

The fact they heard you showering is really not relevant. They don't have to take that hint. They felt they didn't need to shower and that's their personal choice. It affects your housekeeping, yes, but if that trumps your visiting with them, then don't continue visits that involve overnights at home.

Just FYI, I do know a couple of people who say that if they shower at night, especially later in the evening, the shower wakes them up to the point they find it very difficult to sleep afterward. Your friends may be like this. That doesn't account for the lack of a morning shower, I'd agree, but at that point they had already slept on your sheets, so why worry about an a.m. shower anyway?

Just an added note...they may think they are doing you a favor. Sometimes when we visit my sister in law four hours away, we skip showers at her house and clean up when we get home. With four of us and the way my hubby lingers in the shower, we don't want to add to their water bill. And they do the same thing when they come here. Our visits are almost always just one night. (But I think we all take quick, rinse off the funk showers, if we were out an about and got stinky and sweaty. ;) ) Though it is grossing you out, maybe they think they are being considerate.

I wouldn't say anything more. If you hadn't already already asked them several times I'd go with the suggestion of leaving the towels in the room for them. I think at this point, you just let it be in order to be a good host.

I totally agree with AKmom. I would be pissed if you kept asking me if I needed towels, assuming that I did. Why didn't you just lay them on the bed when they got there so they can use them as needed? What if the opposite happened and each of them took 3 showers a day? Would you complain about them using too much water and getting too many towels dirty? If they don't live up to your expectations for them, then don't have them over any more. JMO. Good luck.

I don't think I would want anyone staying in my house that I didn't feel comfortable enough to say that to, but I haven't been in that situation. We always stay in hotels when we travel and I always hope any guests we have will, unless I specifically invite them to spend time with my. My whole family prefers hotels though, so it's unspoken. My MIL is the only one who stays with us and she bathes regularly, so I don't know.

I agree with others who say to put the items out that they need.

Did they smell when they first got to you? Some people just "wash up" so maybe they did that?

I'd make a big deal out of saying:

"Gosh it was sure hot out there today!!! I'm going to go take a shower. MAN! I smell ripe! I'll see you guys in a little, there's plenty of hot water for us all! If you need anything for your showers let me know. I think I covered all the bases."

Then buy a waterproof mattress pad for your bed. THEN put a regular one over that. The plastic backed mattress pad's are like laying on a plastic sheet and that's hot and makes a person sweat all night and not sleep well. They are miserable if they don't have an additional cover on top of them. I have a waterproof cover that is several inches thick (Pillow top) and it's still hot. So cover it too. Or buy a cheap waterproof mattress pad that's thin then put a pillowtop mattress pad cover on top of that.

Put a mattress protector on the mattress.

nothing wrong with offering towels, I feel like that is a good hostess type of thing to do. I wouldn't worry about the mattress though, I would highly recommend the mattress protector, everyone has different levels/expectations of hygeine.

Some people do a really good job with a washcloth! :)