**Core Concept**
The patient's presentation of fever, sore throat, malaise, and cervical lymphadenopathy after being diagnosed with streptococcal pharyngitis suggests a possible complication of the infection. This scenario is a classic setup for a condition that occurs due to an immune-mediated response to the bacterial infection.

**Why the Correct Answer is Right**
The patient's symptoms and history are highly suggestive of erythema multiforme (EM), a hypersensitivity reaction that can be triggered by various factors, including infections like streptococcal pharyngitis. EM is thought to result from a cell-mediated immune response, where T lymphocytes recognize antigens from the infecting organism and trigger a cascade of events leading to the characteristic skin lesions. The rash in EM typically appears as target lesions, which are concentric rings of different colors.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the rash described in the scenario does not match the typical presentation of a viral exanthem. Viral exanthems usually have a more widespread distribution and are not typically associated with a previous history of streptococcal infection.

**Option B:** This option is incorrect because the rash is not consistent with a contact dermatitis. Contact dermatitis is a type IV hypersensitivity reaction that occurs after exposure to an allergen or irritant, and it typically presents with a localized rash and itching.

**Option C:** This option is incorrect because the rash does not fit the typical presentation of a drug rash. While drug rashes can occur after the initiation of antibiotic therapy, the rash described in the scenario is more consistent with an immune-mediated response to a bacterial infection.

**Option D:** This option is incorrect because the rash is not a characteristic of a bacterial folliculitis. Folliculitis is an inflammatory reaction to a bacterial infection of the hair follicle, and it typically presents with small, painful pustules on the skin.

**Clinical Pearl / High-Yield Fact**
In patients with a history of streptococcal pharyngitis, it is essential to consider the possibility of erythema multiforme as a complication of the infection. This condition can be triggered by the immune response to the bacterial antigens, and it requires prompt recognition and treatment to prevent further complications.

**Correct Answer:** C. Erythema multiforme.