**Core Concept**
Epidemic dropsy is a condition caused by the consumption of mustard oil adulterated with argemone oil (Argemone mexicana), which contains a toxic alkaloid called sanguinarine. This alkaloid affects the cardiovascular system, leading to peripheral edema and other systemic complications.

**Why the Correct Answer is Right**
Sanguinarine in argemone oil is a potent inhibitor of the enzyme acetylcholinesterase, leading to an accumulation of acetylcholine in the synaptic cleft. This results in overstimulation of the muscarinic and nicotinic receptors, causing vasodilation and increased capillary permeability. The increased capillary permeability leads to fluid leakage into the interstitial spaces, resulting in peripheral edema.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because epidemic dropsy is not caused by a viral infection, and its symptoms do not match those of viral illnesses.
**Option B:** This option is incorrect because argemone oil is not a known allergen, and the condition is not an allergic reaction.
**Option C:** This option is incorrect because mustard oil itself is not toxic, and its adulteration with argemone oil is the primary cause of the condition.

**Clinical Pearl / High-Yield Fact**
Epidemic dropsy is a classic example of a condition caused by food adulteration, and its diagnosis can be confirmed by the presence of sanguinarine in the patient's serum or urine. This condition highlights the importance of food safety and quality control measures in preventing such outbreaks.

**Correct Answer:** D.