If you want to dress your dog in an outfit, please make should make sure your dog is comfortable. Dogs will communicate this with their bodies. Some signs of a happy dog are: relaxed body muscles; loose lips or even open mouth with loose tongue; rhythmic panting. Some signs that a dog is not comfortable include: his tail may be down, his body may be tight, he may have a tense mouth, you will see the whites on the sides of his eyes, his ears may be back, he may yawn or lick his chops, he may do a body shake without being wet. If wearing an outfit causes your dog to feel stressed, he may be more likely to become reactive – especially when on a leash, in the dark, with so many strange sights and sounds and kids running around.