Generally harmless to humans, Boxelder bugs are nuisance pests, as they gather in large numbers on the warm walls of a home or business.
Besides the nuisance of large swarms, boxelder bugs can be a major nuisance to our pets. If a dog eats a boxelder bug, it will surely vomit and possibly salivate excessively. Cats, on the other hand, appear to enjoy eating boxelder bugs. However, they will likely vomit, as well.