Diagel Diarrhea Control Gel for Dogs (Large) 5 mL Syringe A veterinarians first choice for treating bacterial diarrhea. Unique, palatable formulas for dogs, works within 24 hours. Diarrhea Control is an orally administered product to aid in controlling diarrhea symptoms such as E.Coli and Salmonella in the upper GI tract. These causes include: Diet and/or water changes, Environment changes, Stress, Food allergies, Indiscretions in diet. A one-time dosage should firm stools within 24 hours.