my son is 5 years old. he has been having prolonged colds since he was a year old. over the time he has had his tonsils and adenoids removed, this hasn t help however. also over the last four years he has developed a recurring rash on his neck that looks like acanthosis nigricans, i thought it was eczema. could it be caused by the different cold medicines he has been taking? the medecines he takes most often are Histal DC, histatussin, in april 2014 prednisolone, and more recently bisolvon