An abscess tooth untreated for many years can cause bodily infections, but can it cause asthma-like symptoms (excessive mucus, airway constriction) ?

DENTAL ABSCESS : Any infection can precipitate asthmatic attack. It depends on the allergen causing it. Most probably infection first before the asthma.

It is a possibility: The bacteria from an infected gums travels through the blood stream to other areas/organs of the body can cause bacteremia (bacteria in the blood) can also make you generally ill, effect any body system and cause cause asthma-like symptoms. Regular dentist visits can do more than keep your smile attractive, it may prevent general health problems.