I Have A Three Year Old Autistic Child (who Doesn't

I have a three year old autistic child (who doesn't talk much) when he does speak he especially in the morning he sounds hoarse. For the past week he has been unusually clingy he has also had a runny nose and has been displaying allergy like symptoms. His nose has been running so badly that his face is constantly covered in snot. I have been giving him benadryl to help with that. Tonight I noticed that he is sweating from the head excessively yet he does not have a fever. I have changed his pillow twice in two hours. What should I be watching for if anything?