Hi, Welcome to Healthcare magic. the symptoms you are having are indicative of type-1 hypersensitivity reaction which are acute life threatening phenomena with fall in blood pressure and angioedena and glottic swelling which can cause unconsciousness and choking. Likely cause is an environment allergen- can be a pollen, dander, mite, cyanodon, house dust or articles of day to day use like deo, creams, oils, soaps etc, sometimes sea foods may be a cause. I will suggest you to be watchful about the exposure that starts or aggravates the symptoms, it will help you locate the culprit and avoid it in future. Meanwhile you should be on antiallergic medicines to remain safe. I hope the advise will be helpful for you. If you want any further clarification or follow up you can put query in my name. Take care.