My 3 Year Old Has Mucus From Allergies Or A

My 3 year old has mucus from allergies or a cold that makes her vomit. She has an aversion to oral medicine. It will make her vomit every time. What can I give her to stop the mucus running down her throat? Is there a suppository or something other than an oral medication? She has ended up in the hospital two times in the last year for dehydration. I really need to stop this vomiting. She does not have diarrhea.