Why is my dog suddenly aggressive at the dog park?

Sudden aggression in dogs can indicate underlying medical or behavioral issues, and consulting a veterinarian is crucial. Various health problems, such as hypothyroidism or dental issues, can manifest as aggression in dogs. Fear can prompt sudden behavior and temperament changes like aggression. Temporary aggression may stem from your dog reacting to a perceived threat. An injury could be the source of your dog's sudden aggression, and something you might not have realized your dog experienced because of their ability to hide pain. To explore this possibility, start with a cursory physical exam. Look for swelling, cuts, torn paw pads, insect stings, or tender spots. Anything that looks out of the ordinary could be hurting your dog and causing aggression. Health Problems or Illnesses can also affect your dog's personality, and some can be serious, such as canine cognitive dysfunction or dementia, or brain damage to specific areas of the brain from tumors, thyroid issues, and trauma.