There are several potential reasons why your dog may lick your pillow:

1. Taste: Dogs have an acute sense of taste and may lick objects that have a distinct flavor or scent, including your pillow. If your pillow has a particularly strong smell or taste, your dog may be attracted to it and lick it as a result.
2. Comfort: Some dogs may lick objects as a way of self-soothing or seeking comfort. Licking your pillow may be a way for your dog to relax and feel calm.
3. Attention seeking: If your dog licks your pillow while you are nearby, it may be a way of trying to get your attention. Dogs are social animals and may lick objects as a way of seeking interaction with their owners.
4. Obsessive behavior: In some cases, excessive licking of objects may be a sign of obsessive-compulsive disorder (OCD) in dogs. If your dog’s licking is excessive or appears to be uncontrolled, it may be a good idea to consult with a veterinarian or a professional animal behaviorist.
5. Medical issues: Licking can also be a sign of an underlying medical issue, such as allergies or a skin condition. If your dog’s licking is accompanied by other unusual behaviors or symptoms, it is important to have them checked out by a veterinarian.

Overall, the reasons for your dog licking your pillow may be benign or may indicate a more serious issue. If you are concerned about your dog’s licking behavior, it is important to consult with a veterinarian or a professional animal behaviorist for a proper evaluation and guidance.