Here’s the trick to that.

It’s their body, so they have a say in things. Ideally, anything that’s about their body would be their choice, but some stuff just isn’t realistic, like medical decisions as one example.

However, they’re also going to deal with the fallout of such decisions.

A lot of kids, not just boys, go through a phase where they reject the seemingly arbitrary enforcement of hygiene standards.

So, when they make an adult decision, they can deal with adult consequences.

You aren’t required to sit in a car with someone that smells unpleasant. Nor at a dinner table, or on the couch.

Now, if them not using a given product doesn’t cause them to smell bad, there’s zero harm in it, so a parent would be a dick for trying to enforce an unnecessary thing, even by that method. If you’re trying to enforce pointless things, you’re fighting the wrong fight. Believe it or not, deodorants and antiperspirants aren’t the only way to keep oneself from smelling bad, and not using them doesn’t always result in an unpleasant smell. There’s a lot to be said for just bathing daily and giving the pits and crotch a scrub when you’re in the bathroom for other things

However, if they aren’t willing to do what it takes to not stank, remind them that adult choices have different consequences, and that you aren’t obligated to take them places, let them use your vehicle, sit around the dinner table with everyone else, snuggle on the couch for movies, or even sit on the couch at all. You can also enforce that they clean their private spaces (bedroom or other spots that they have where they have an expectation of privacy) more often so that those places don’t start to smell bad either

A stanky adult is quickly going to discover that people don’t want them around when they stank. Might take a while for friends and family to start objecting seriously, but out in the world, it can happen fast.

But respect body autonomy while doing so. It really, truly is something that they need to have. And it’s important to teach them that they should be able to expect body autonomy, even when there are consequences to some of the choices made.

It works. I’ve seen it work dozens of times, because I come from a big extended family that used to spend a lot of time together. Every generation of kids, there’s going to be a handful of them that express their body autonomy like this. Maybe it’s not bathing, maybe it’s deodorant, or hair washing, or a clothing issue. Staying gentle, but not backing down about it, you both keep their trust, and show them that every choice has consequences, even if tiny ones.

My personal phase, it was very effective. My grandmother, if I was smelling rough, would tell me to go wash up as soon as I walked in the door. After the first few times, it was “you know where the washcloths are.” If I didn’t wash, I could bloody well sit outside if the weather was safe. My mom and dad enforced similar boundaries.

Took maybe a couple of days before I got the point, and a couple of weeks before my stubborn ass decided they had a good point, and improved my routine.

Will it absolutely work for everyone, every time? Of course not. But it’s a gentle way that helps foster a sense of self control, of having a say in their life, as they’re needing to explore who they are the most. The key though, is gentle but firm.

You don’t say “you stink, go away” or some shit. You say “washing up is mandatory if you want to sit with the rest of us.” You make it a choice, if a limited one. Give them as many options as possible, too. If they’re objecting to deodorant in specific, maybe offer washing up, or changing clothes if the smell is more from that.

In other words make it about the actual problem rather than them. It isn’t that they’re bad or dumb, or anything else like that. It’s that personal hygiene is important for skin health, and social interactions. They don’t necessarily have to shower to be clean. They don’t have to use deodorant to not smell bad, or to smell good. So present them with alternatives after figuring out why they don’t want that specific method