Is it possible to be allergic to a drug, not metabolize it, or w chemical used titanium dioxide is in question for severe allergic asthma. ?

Highly unlikely: Titanium may potentially cause a systemic contact allergy but this is far from proven but I know of no known mechanism for it to cause severe asthma. I hope you are under the care a B/C allergist. If he cannot help you, consider consult at a specialty asthma center. If you have failed all medications, then need to reassess the diagnosis. Vocal cord dysfunction is just one such possibility.