**Core Concept**
Epinephrine is the primary treatment for anaphylaxis due to its rapid onset of action in relieving symptoms such as bronchospasm, hypotension, and mucosal edema. Its mechanism involves stimulating alpha-adrenergic receptors to cause vasoconstriction, which increases peripheral resistance and blood pressure, and beta-adrenergic receptors to cause bronchodilation and reduce histamine release.

**Why the Correct Answer is Right**
Epinephrine, administered via intramuscular injection, works by rapidly increasing blood pressure through vasoconstriction, thereby improving cardiac output and oxygen delivery to vital organs. It also causes bronchodilation, which relieves respiratory distress, and reduces mucosal edema, which facilitates breathing. The rapid onset of epinephrine's effects makes it the drug of choice for treating anaphylaxis.

**Why Each Wrong Option is Incorrect**
**Option A:** Antihistamines, such as diphenhydramine, are not the primary treatment for anaphylaxis due to their slower onset of action and limited ability to reverse severe symptoms like bronchospasm and hypotension.
**Option B:** Corticosteroids, such as prednisone, are used to prevent late-phase reactions and reduce inflammation but do not provide immediate relief for acute anaphylaxis symptoms.
**Option C:** Bronchodilators, such as albuterol, are useful in relieving bronchospasm but do not address the underlying pathophysiology of anaphylaxis and are not sufficient as monotherapy.

**Clinical Pearl / High-Yield Fact**
When treating anaphylaxis, it's essential to remember that epinephrine is the drug of choice due to its rapid onset of action and ability to address multiple symptoms simultaneously. A second dose of epinephrine may be required if symptoms persist or worsen after 5-15 minutes.

**Correct Answer:** C. Epinephrine