Localized varicella has been associated with UV-exposure and skin trauma. Varicella restricted to a pre-existent dermatitis is exceptional.The clinical features, cytohistologic and immunohistochemical results, as well as serologic data of 6 patients with a sudden eruption of vesicular and eroded lesions restricted to a pre-existent dermatitis are presented.All patients (mean age: 8,3 years, range: 3-22) showed crops of a few to numerous vesicular lesions clustered on the restricted sites of posttraumatic wound, perianal streptococcal dermatitis, dermatomycosis, allergic contact dermatitis, lichen sclerosus, and atopic foot dermatitis. All the Tzanck smears and 1 biopsy revealed multinucleated giant cells, consistent with herpes simplex virus (HSV) or varicella zoster virus (VZV) infection. Immunohistochemistry using specific anti-VZV antibodies (IE63 and gE) was positive on all the smears and the biopsy, whereas HSV-I and HSV-II immunolabeling was negative. VZV specific IgM+, IgG- EIA-based serology, and positive VZV-specific IgM complement fixation test suggested primary VZV infection. None had received varicella vaccine. None of the patients presented a history of varicella nor experienced breakthrough varicella. It was decided not to administer antiviral treatment, as the varicella lesions remained localized without any further skin extension and systemic signs. About 2 months later, EIA-serology revealed positive VZV-IgG and negative IgM levels in 5/5 patients.Some patients have varicella infection that remains hidden in a pre-existent infectious and/or inflammatory dermatitis without ever presenting full-blown chickenpox. The sudden occurrence of vesicular and/or ulcerated lesions on a pre-existent dermatitis should prompt searching for a viral infection.