Some silly Omegaverse thoughts
You know the bee attack pheromone that tells other bees to target someone? Omegas can do that. It's jokingly referred to as Alpha B'Gone because it has an actively repellent effect on Alphas, but of course it's not like an Omega can't smear the scent on a Beta or even another Omega if need be. They won't be repelled by it, but it will signal to everyone who smells it on them that they have pushed an Omega to that extreme amount of stress and fear.
The smell is a big deal. It's basically an aggro spell. It paints a target on the person who's been marked and tells everyone else to Get His Ass. Most people can't consciously control it, but the people who can do not use it lightly.
Except of course for Omega Zoro, who will sometimes skunk spray Sanji when he's being especially annoying. Sanji, understandably, hates this. He has kicked the shit out of alphas for coming into the Baratie with this scent on them, and now here he is staring at himself in the mirror, trying to come to terms with what his life has become.
The crew is four days out from their next destination, which should be more than enough time for the scent to fade, so Zoro hits Sanji with the Fuck You Fuck Off spray a little after breakfast, only for the Strawhats to stumble across an island too small to have it's own magnetic field. Everybody else gets to go explore and make friends with the locals and have an adventure but Sanji needs to stay on the ship for his own safety.
Zoro does genuinely feel bad! But not bad enough to stop doing it.