Pets, especially dogs, are at risk of chocolate toxicity, xylitol poisoning, and gastrointestinal issues from candy wrappers. Symptoms of chocolate poisoning include vomiting, diarrhea, tremors, and seizures, while xylitol can lead to severe liver damage and hypoglycemia. Stress from Halloween activities, such as doorbells and unfamiliar visitors, can also negatively affect pets. These risks highlight the importance of vigilance and preventive measures to ensure pet safety during the holiday.