Why does my dog only growl at one person?

Dogs may growl at a specific person due to feeling threatened, fearful, or uncomfortable around that individual. It could be a result of past negative experiences, lack of socialization, or a specific behavior or scent that triggers the dog's defensive response. It's important to observe your dog's body language and behavior to understand the underlying cause and address it appropriately. Consulting with a professional dog trainer or behaviorist can also help in resolving this issue.