Matt: Seizures cover a huge topic, and can be either environmental, genetic, or require an interaction of the two. For instance, convulsive seizures seen in puppies are usually from exposure to toxins or certain illnesses. Seizures (grand mal- convulsive or petite mal- non-convulsive) in old dogs is often from a brain tumor. Seizures at 2-3 years though that happen often enough to be considered epilepsy are generally listed as 'primary epilepsy (which is a broad term that covers what our dog had). He was half cattle dog and half Australian shepherd, and we found out that epilepsy (including the degenerative kind he had) is abnormally high in some Australian shepherd lines. So for him, it was genetic, though the exact cause is not known. In other dogs though, food allergies can set off seizures and epilepsy (generally grand mal), as can vaccines/stress/heat/etc., and that is probably a case of genes interacting with environment.