Rupturing of the infected cells cause a great number of viral particles to be released, rendering them the ability to affect adjacent epithelial cells and even the sensory axons of the trigeminal nerve. Histologically, these infected cells have an eosinophilic cytoplasm and large, pale vesicular nuclei, appearing swollen under the microscope. The cytoplasms of the infected cells fuse, collectively forming giant cells with many nuclei. The balloon cells and multi-nucleated giant cells can often be identified in smears taken from an intact vesicle or from one which has been recently ruptured.