<<Disclaimer: Verify this information before applying it to your situation.>> Will is 3yrs old & has been Diagnosed for about 4 months with symptoms since birth and suspicions of CD since about 20 months old. His Diarrhea is usually filled with more whole foods when it is a Gluten result and has a tendency to burn his bottom quicker than a viral diarrhea. His pediatrician always tests his blood to verify the cause which helps to rule out the gluten reaction. He will not give him an antibiotic unless it is an infection since the antibiotics tend to increase his diarrhea problems. I hope this has been of some help to you. If you discover any other way of determining the difference let me know! Thanks, Peggy