Dogs can have nightmares, but they are not likely to dream about the same things that humans do, such as showing up to school naked or losing all of their teeth. Instead, dogs tend to dream about activities they often do, such as running or pointing at birds. The content of a dogs nightmares can vary depending on the dog, but any situation that causes stress or anxiety for the dog could lead to nightmares, such as nail trims, grooming, stress at the vet, and more. If a dog is having a nightmare, they are most likely recalling a traumatic experience. Dogs who have experienced more trauma in the past are more likely to have nightmares. If a dog is in the middle of a nightmare, its important not to wake them up unless absolutely necessary, as doing so may startle them and cause them to lash out. Most nightmares only last a few minutes, and dogs will often return to a restful sleep in no time at all. To help prevent nightmares, making a comfortable environment can be a preventative measure. Playing quiet music, providing a crate to help the dog feel safe in a "den," or trying a pressure wrap can help.