After some speculation as to what ailment caused the breathing difficulties Cardinals closer Carlos Martínez had been experiencing, the St. Louis Post Dispatch has delivered a definitive answer:
It is allergies.
Anyone in St. Louis right now can attest that the air quality can get pretty rough. It also turns out Martínez has asthma, which he was previoulsy unaware of having.
This is ultimately good news for Martínez and the Cardinals as both allergies and asthma are common and pretty easily treatable. Martínez has already been cleared to play.