There is a whole list of typical smells which can give a clue of the medical diagnosis.

Below just one example which is not relevant today because all newborns are tested for phenylketonuria (PKU)

The musty smell of new-mown hay is supposedly characteristic of phenylketonuria (PKU). The odor of PKU has also been described as like that of stale, sweaty locker-room towels, or as wolflike or barny (Liddell, 1976). The apocrypha of my student days taught me that the mother of the first child diagnosed as having PKU took the child from pediatrician to pediatrician, complaining that the child smelled “musty, like a mouse.” Each dismissed her as unbalanced, until Dr Folling finally agreed to smell the child before laughing at its mother. To his surprise, the child indeed smelled musty, like a mouse. Because of the train of events that he set in motion, the mandatory testing of our day makes it unlikely that anyone will have to smell that particular odor again.

Orient, Jane M.. Sapira’s Art and Science of Bedside Diagnosis . Lippincot (Wolters Kluwer Health). Kindle Edition.