Difference in BP during Anaphylaxis VS Acute Myocardial Infarction

With regards to allergic reactions, as far as I have studied, Acute Myocardial Infarction dramatically increases blood pressure due to severe vasospasm and thus potentiates the AMI. However, during an Anaphylactic Shock there is a severe decrease in blood pressure. I know very little when it comes to what the difference is that would make one allergic response cause high blood pressure and the other low blood pessure. Would someone please be able to tell me what causes the difference in BP? I am aware that histamine causes the dilation of blood vessels during the anaphylactic shock, but it doesnt really explain to me the core difference that makes the reactions vast. Is it due to different allergens or due to individual reactions to allergens? etc. Thanks!

[Dr_Aparna]

Hi,
Anaphylactic shock, the most severe type of anaphylaxis, occurs when an allergic response triggers a quick release from mast cells of large quantities of immunological mediators (histamines, prostaglandins, leukotrienes) leading to systemic vasodilation (associated with a sudden drop in blood pressure) and edema of bronchial mucosa (resulting in bronchoconstriction and difficulty breathing). Anaphylactic shock can lead to death in a matter of minutes if left untreated.
Anaphylaxis is a life-threatening medical emergency because of rapid constriction of the airway, often within minutes of onset, which can lead to respiratory failure and respiratory arrest.
AMI is not a response to an allergy but is caused by arterial blockade by a blood clot.
Any allergic comlpication of the heart stems from the low BP.