Slugs are not dangerous for dogs to eat under most circumstances. However, when slugs have been exposed to a poison bait, they become extremely dangerous. If a dog consumes poisoned slugs, then medical attention is needed immediately.
Most baits to control slugs contain the highly toxic poison, Metaldehyde. When a dog eats a poisoned slug, the poison takes effect anywhere between one and four hours after consumption. Symptoms of poisoned slug ingestion include panting, drooling, vomiting and becoming uncoordinated, as well as nervous. The poison is capable of inducing a high spike in temperature, up to 108 degrees Fahrenheit, which is hot enough to cause permanent organ damage.