Dogs have extraordinary noses. They can smell explosives and accelerants for arson, and the tiniest traces of narcotics, no matter how well masked or concealed. With a sniff, they can tell whether a new friend at the dog park is male or female. They can even catch the aroma of disease, including cancer, diabetes and, it turns out, epileptic seizures. Epilepsy is one of the most common neurological diseases in the world. In the United States, it afflicts nearly 4 million people. Worldwide, this number reaches 50 million. Though epileptic seizures seem to come on suddenly, without warning, subtle clues emerge ahead of the attack via changes in scent: The body releases volatile organic compounds, or VOCs?"molecules that can travel through the air. Dogs can detect these VOCs about 15 minutes before a seizure begins and alert their companions.