Injury to the brain from trauma, low blood sugar, poisons, or organ problems can bring on a seizure. Some seizures have not identifiable underlying cause. They are usually a result of abnormal electrical activity in the brain. Although they may look scary they usually will only last a few seconds or minutes. Seizures themselves generally aren't dangerous unless they last longer than 5 minutes. Make sure to have your pet fully examined to determine the cause of the seizure especially if this is their first time having one. There is medication available to help control seizures.