Does activated charcoal make dogs vomit? It is possible that activated charcoal could cause vomiting in dogs, but not all dogs will have this side effect or any at all. Side effects of activated charcoal can also be mild and may include black feces, vomiting, eye irritations, diarrhea ... Answered By: Lon Romaguera. Date created: Wed, May 12, 2021 12:02 AM. Activated charcoal already has a ...