They are not appropriate places to socialize a dog. Many dogs aren’t comfortable being in groups of unfamiliar dogs. Encountering groups of other dogs all focused on you can be overwhelming and frightening for a socially unskilled dog, especially a young one. If your dog isn’t socially skilled or mature, letting them run free in a dog park could lead to behaviour problems. Your dog could be intimidated or bullied by other dogs and your dog, unsure how to respond, could start acting defensively or bullying other dogs, too. Dogs who are fearful or shy under the age of 2, females in heat, easily over-aroused, dog selective, resource guarders, fence runners, prone to barrier frustration, or any with a bite history are likely to be anxious, frustrated, defensive or hyper-vigilant in a dog park. Many dogs who aren’t comfortable in a dog park can experience trauma which may not be detected by their owners but will impact their future behaviour especially if they’re young and still maturing. Not all friendly dogs have been socialized with children or are comfortable with children, for everyone’s safety, best to save time with children for leashed or trail walks where dogs are more closely monitored.