**Core Concept**
The question requires the application of dermatological knowledge to diagnose a skin condition in an infant. The **clinical presentation** of itchy erythematous papules, exudative lesions, and vesicular lesions on specific body parts suggests an allergic or infectious etiology.

**Why the Correct Answer is Right**
Given the description, the most likely diagnosis is **scabies**, a parasitic infection caused by the mite **Sarcoptes scabiei**. The presence of vesicular lesions on the palms is a characteristic feature of scabies in infants. The distribution of lesions in the scalp, face, groins, and axillae also supports this diagnosis.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because the description does not match a typical viral exanthem.
**Option B:** Incorrect as it does not typically present with vesicular lesions on the palms.
**Option C:** Incorrect because the clinical presentation does not align with a bacterial infection.

**Clinical Pearl / High-Yield Fact**
Scabies in infants often involves the scalp and face, which is less common in adults, and the presence of vesicular lesions on the palms is a distinctive feature.

**Correct Answer:** D. Scabies.