What Causes Tight Throat, Breathing Issues With Dizziness?

THE OTHER DAY ALL OF A SUDDEN I HAD A HARD TIME BREATHING, MY THROAT TIGHTENED UP AND I FELT LIGHT HEADED AND DIZZY AND IT DID NOT GO AWAY SO I WENT TO THE EMERG RM. THEY GAVE ME TWO BREATHING TREATMENTS AND 3 PRETHNAZONE PILLS..AFTERWARDS I BEGAN TO BREATHE NORMALLY. THE DR SAID I HAD A COLD. I'VE HAD A COLD NUMEROUS TIMES BUT NEVER HAD SHORTNESS OF BREATH. WHAT COULD HAVE CAUSED THIS?