How Should I Treat My Toddler’s Raspy Voice And Chest Rattle While He’s On Medication For Strep Throat?

For the past 3 days my 4 year old son has had a raspy voice and a chest rattle when he sleeps. He is not congested. However, he coughs once in a while. No flem or mucus. He is currently taking medication for strep throat. How should I treat his raspy voice and chest rattle? Any over the counter medication?