There is no definitive answer to this question as it depends on the severity of the injury and the dog's personality. Generally, if a M&M is dropped on a dog's head, it will likely cause some type of injury. However, some dogs are so resilient that they never seem to suffer from M&Ms, while others are so allergic to them that they become violently ill if they ever consume them. Ultimately, it is up to the dog's owners to decide if they want to give their pet the M&M experience or not.