medicine smell

My son has a very deep and weird medicine odor coming from his body and sometimes his mouth.  One day he was sitting in my car, smelled fine, and then all of a sudden I smelled a medicine odor coming from his body and then it stopped- almost as if the body was undergoing some kind of automatic process of which my son has no control over.  It seems that this odor is unrelated to eating because it can occur before or after he eats.    I am very concerned that he could have some kind of fungal or bacterial infection because he has been on accutane for 4 months and now doxycline for over a year for cystic acne.  

Any help as to what kind of condition my son might have, what kind of tests he should request or what kind of doctor he should see?  I have smelled this on and off odor for over 6 months now.  He is 20 years old.

Very concerned Mom