The diagnosis is made by observing the symptoms and the typical appearance of the rash.
The blisters are like dew drops on the petal of a flower. Except that the dew drop is on a background of red rash.
Laboratory diagnosis is seldom required because of clear-cut clinical signs.
Examination of the fluid present within the lesion under the microscope shows characteristic round particles. Scrapings from the floor of the lesion show, what are called, giant cells.