Difference Between Small Pox and Chicken Pox Difference between chickenpox and smallpox is tabulated below Feature Smallpox Chickenpox Caused by: Smallpox is caused by the Variola virus Chickenpox is caused by Varicella zoster virus Incubation Period: It is 7-17 days for smallpox It is 7-21 days for chickenpox Prodromal Symptoms These are Severe in smallpox These are Mild in chickenpox Distribution Of Rash Centrifugal for smallpox Centripetal for chickenpox Palms and Soles Frequently Involved in smallpox Seldom affected in chickenpox Axilla Usually free in smallpox Axilla is affected in chickenpox Rash In smallpox it is Predominant on extensor surface, deep-seated, vesicles are multilocular, only one stage of rash is seen at one time and there is no inflammation around the rash. In Chickenpox Predominant on flexor surface, Superficial, Vesicles are unilocular, dewdrop li