Differences between chicken pox and small pox
| Small pox | Chicken pox | |
| Incubation period (approximately) |
12 days | 15 days |
| Prodromal symptoms | Severe | Mild |
| Rash – sites affected | Extensor surfaces, palms, soles | Flexor surfaces, axilla |
| Rash – features | Deep seated | Superficial |
| Single stage or rash present at a time | Multiple stages of rash at the same time (pleomorphic) | |
| Multilocular, umbilicated vesicles | Unilocular vesicles, classically ‘dew drop on rose petal’ | |
| No inflammation around rash | Zone of inflammation present around rash | |
| Rash – evolution | Slow, all stages are visible | Fast evolution of rash |
| Scab formation by 10-14 days of disappearance of rash | Scab formation by 4-7 days of disappearance of rash | |
| Fever | Fever subsides with development of rash, may appear again with formation of pustules (secondary rise of temperature) |
Fever occurs with each crop of vesicles |
