Which of the following would block the original signal that leads to vasodilation associated with an allergic response? Corticosteroids
Epinephrine
Immunosuppressive Medications
Antihistamines

The correct answer is - antihistamines.

Explanation:

Histamine is an organic chemical compound that triggers vasodilation and increases heart rate, vascular permeability, glandular secretion, and cardiac contraction that are associated with the allergic response.

Antihistamines are the class of drugs used to block the effects of histamine in allergic responses by blocking the original signal that leads to vasodilation which is triggered by histamine if any infection is found by the immune system.