#Aloe Vera posses many benefits for human beings. However, depending on ingestion can be very toxic to dogs! Inside this common house plant is anthraquinone glycosides which are purgatives (medication that helps encourage vowel movements). When ingested the glycosides are metabolized by intestinal bacteria forming compounds that increase mucus production and water in the colon which will cause vomiting and diarrhea which are both life threatening because they can cause dehydration.
Harsher symptoms that can play a part from a higher ingestion are: Depression, anorexia, changes in urine color, and (rarely) tremors.
To conclude: ingesting Aloe Vera is more on the mild to moderate side of things depending on how much, but I would still keep this houseplant away from your animals. If you see your dog ingest contact a veterinarian and see what needs to be done.