My dog’s eye has been bruised, swollen, and purple. It keeps shaking its head and is vomiting.

Hello, based on your brief description I can’t make an accurate diagnosis. From the photo you uploaded, the dog doesn’t appear to have a serious problem, but without knowing its medical history or how long the symptoms have lasted, I can only judge that the head-shaking and vomiting are caused by a bump or possible poisoning.

If the dog’s head was struck and caused a concussion or head injury, it could lead to local swelling and vomiting. The owner should take the dog to a veterinary clinic for a thorough examination and targeted treatment based on the results.