My son has just noticed a rattle that won t clear through coughing. He has had no cough or illness sytoms, with fever . He has also just finished a course of penicillin for tonsillitis last week. He is 10? About 3 yr ago he had inhalers for a persistent cough during winter and had been told he could be borderline asthmatic but it was the one and only time he has ever needed them in his life ??? Thanks