- Caused by the viruses HSV-1 (generally causing herpes labialis, transmitted by oral contact) and HSV-2 (generally causing genital herpes, sexually transmitted)
- Grouped, painful, tense vesicles on an erythematous base
- Following the acute eruption, latency occurs in the dorsal root ganglia, and recurrent outbreaks may occur throughout the life of the patient.
- "Steel gray" keratinocyte nuclei
- Multinucleated keratinocytes with margination of chromatin ("pomegranates")
- Eosinophilic nuclear inclusions surrounded by clear haloes
- Intracellular edema and ballooning degeneration
- Intraepidermal vesiculation
- Dense mixed dermal infiltrate consisting of lymphocytes, neutrophils and eosinophils
- Sometimes inflammation of nerve twigs and/or vasculitis is seen.