Final answer:
In the case of anaphylaxis, epinephrine is always the first medication to be administered due to its rapid effects on reversing the dangerous symptoms of this severe allergic reaction.
Step-by-step explanation:
When a patient develops diffuse flushing of the skin and angioedema following a medication infusion, it is crucial to recognize these symptoms as potential indications of anaphylaxis, a severe and life-threatening allergic reaction. The immediate administration of epinephrine is the first-line treatment, as it works quickly to counteract the effects of the anaphylactic response by constraining blood vessels to increase blood pressure, relaxing smooth muscles in the lungs to improve breathing, regulating heart rate, and reducing swelling. Other medications like antihistamines, corticosteroids, and bronchodilators do have roles in managing allergic reactions but are not as immediately critical as epinephrine in the acute phase of anaphylaxis.