A skin biopsy specimen demonstrated a mild superficial perivascular lymphoeosinophilic infiltrate, consistent with a hypersensitivity reaction, such as to an arthropod bite or infestation. A few histiocytes were also seen. Despite histologic examination of multiple hematoxylin-eosin–stained sections, no caterpillar spines, arthropod parts, or other foreign objects were identified.
Our patient had minimal symptoms at the time of his initial visit (7 days after being stung), so we prescribed twice-daily applications of fluocinonide ointment. He noticed a slight improvement of his condition within 5 days and complete resolution 16 days later.
Erythematous Papular Rash on the Upper Back Area—Diagnosis. Arch Dermatol. 2006;142(11):1501-1506. doi:10.1001/archderm.142.11.1501-f