- The most common rash in dengue fever is a maculopapular rash, which typically appears 3–4 days after the onset of fever.
- This rash results from immune-mediated vascular endothelial damage causing increased capillary permeability.
- It often starts on the limbs and trunk and may be associated with mild pruritus.
- Unlike vesicular or urticarial rashes, the maculopapular rash is non-vesicular and non-blanching initially but becomes blanching as it evolves.
- Petechial rash may also occur but is less common and indicates thrombocytopenia and capillary fragility rather than the typical presentation.
- Thus, the maculopapular rash is the characteristic dermatological finding in dengue fever.

Reference: Davidson’s Principles and Practice of Medicine, 23rd Edition, Chapter: Tropical Medicine, Page 834.