How to treat a 5 year old with runny nose and rash on face that itches

My 5 year old special needs grandson has been treated for a clear runny nose and a rash on his face that he scratches until it bleeds since Sept. 10.  He has been on Claritin, Zyrtec and Cetirizine.  The Claritin works for a short time, The Zyrtec made him very hyper and he vomits up the Cetirizine.  We are now back to the Claritin at 3/4 teaspoon a day.  This gives him some relief but not much.  We have to hold him down and syringe any medicine in him that we give to him.  He is also has PPD-NOS.  He has an appt. with an allergist on Nov. 6.  Do you have any suggestions on any meds to give him or any other ideas on how to help him? He has only been to preschool 10 day since Sept. 10.