It's a question that has been asked many, many times. Do our dogs and cats know when we're naked?
Unfortunately, the answer is kind of unsatisfying.
Dogs, who have co-evolved with humans for thousands of years, are extremely tuned in to changes in their owners. However, those changes might not be ones that are obvious to us humans.
Interestingly, one study found that dogs can tell the difference between different clothing on humans. However, there is no evidence that points to them understanding when we are not wearing clothes. To humans, the difference between a naked person and a clothed person is stark. But to dogs, who have no sense of clothing or modesty (and who are naked pretty much all the time), the difference may not be that obvious — at least not visually.
However, dogs may pick up on a difference via scent. Dogs use their noses more than their eyes to pick up on clues from their environment. They use their powerful sense of smell to detect pheromones, a chemical substance that humans and other animals release. (Pheromones are also the reason why dogs sniff each other's butts!) Humans have large concentrations of pheromones in our genital and anal areas, which is why you may sometimes catch your dog smelling your crotch. When you're naked, your genital and anal areas are more easily accessible, so your dog may come sniffing around for information.
That said, the difference they're noticing does not equate to "my owner is naked" in their dog brains. They might be delighted that they can easily access your pheromone-rich areas, but they don't have anything close to our human definition of nudity.
Cats, who domesticated themselves, are not as obsessively in tune with their human owners as dogs are. However, they're still good observers of human behavior (and they're excellent at knowing when it's dinner time).
So do cats know when we're naked? The answer is ... probably not. Some people have reported that they get weird reactions from their cats when they have a towel on their head, which might coincide with being naked after a shower. In these cases, the cat is probably noticing that you look slightly taller, or that your head has a different shape than usual.
It makes sense that when you add something to yourself, such as a towel, a cat would notice. Other cat owners have observed that their cats don't like it when they wear hats or costume ears.
However, we have no evidence that cats notice humans' lack of clothing, or that they even understood we were wearing clothes in the first place. Like most pets, cats are usually naked themselves, and we have nothing to indicate that they would understand the state of being dressed or undressed.
The only thing your pets might pick up on is your energy if you feel weird about being naked in front of them. If you tense up because you feel awkward, your cat or dog may sense that energy, and seek to find out why you're acting strange. But if you don't feel weird about it, there's no reason not to be naked in front of your pets.
Do you feel your pet acts different toward you when you're naked?