Which childhood disease is characterized by a rash described as "dew drop on rose petals"?

The disease characterized by a rash described as "dew drop on rose petals" is chickenpox. This distinctive description refers to the appearance of the chickenpox lesions, which start as small, red bumps that quickly develop into fluid-filled vesicles. The vesicles are typically round and have a clear, dome-like appearance, resembling dew drops resting on rose petals.

The progression of the rash in chickenpox is a key feature: it initially presents as macules, then evolves into papules, and finally forms vesicles, all while new lesions continue to develop. This creates a characteristic presentation on the skin, often accompanied by other symptoms like fever and malaise.

Other conditions, while they may have rashes, do not present in this particular way. For instance, measles typically has a different rash that starts on the face and spreads downward, characterized by flat, red spots. Scarlet fever is associated with a bright red rash that may feel rough or "sandpaper-like." Hand-foot-and-mouth disease often leads to sores in the mouth and a rash on the hands and feet, quite different from chickenpox lesions. Thus, the unique description of chickenpox lesions makes it the correct answer.