Thought My Son Had Allergies Bec He Has Clear Mucus

Thought my son had allergies bec he has clear mucus and has a history of allergies and asthma and grass/mold/pet allergies. Just moved into a new rental. So his nose started up. Next day it was a headache. Next day no headache just nose. Next day he has a fever (102.0) just have Tylenol due to him hurting/cold/grinding teeth. So now what medicine do I need to give OTC bec we are out of town and insurance is a NO.