Poisoning or toxicity of many different types can result in seizures in dogs, and this is not exclusive to dogs of the Chihuahua breed. However, the amount of any poison or toxic substance required to cause harm to a dog depends in part on the dog’s size, so if your Chihuahua ingest something they shouldn’t or is exposed to poison, they are likely sicker than bigger dogs.
Poisoning with many different toxins can result in seizures, and such symptoms usually develop quickly and are often quite acute. Depending on the type of poison and the systems involved, they could be vomiting, diarrhea, black tarry stools, coughing or vomiting blood, drooling, pale gums, unusual behavior, weakness, bad breath, increased drinking and peeing or decreased/no peeing. Contact your vet as a matter of urgency if you think your dog has been poisoned or eaten something toxic.