How Does Mold Lead To Severe Cough And Pain In Chest?

My son is 19 and has a 35 gallon fish tank in his room, for 3 years, and mold sometimes gets around windows from moisture. he has developed a very phlegm y cough and irritated throat for the last 3 weeks, no fever or body aches or chest pains. could the mold suddenly cause an allergic reaction of this type? never mind he has an appt at doctor tomorrow and wasnt aware of the fee involved. Thanks anyway