My 4yr old is on cefdinir for 10 day for sinus. Day 4, didn't cough in sleep, no more yellow stuff coming from eyes. How long until the infec. Is gone?

Sinusitis. Usually a bacterial infection is better in seven to ten days on antibiotics. Sinus infections, however, when bad can take several weeks to get better. I am happy to hear your son is improving so rapidly.