Reintroducing the Tzanck smear.

The Tzanck smear is a rapid and simple technique that can be performed in the clinic or doctor's office with minimal patient discomfort or cost. It is known to most dermatologists as a rapid test for diagnosing herpes virus infections. Its use, however, can be more widely applied, including in the diagnosis of pustular diseases of the newborn, cutaneous infections, vesiculobullous diseases, and non-melanoma skin cancers. Material is gently scraped from the base of a vesicle, blister, or pustule or directly from the lesion or tumor. Typically, the material is allowed to air dry after which it can then be stained with a variety of stains, including Giemsa, toluidine blue, and methylene blue. The Tzanck smear should not be used to replace more standard diagnostic techniques, but rather as an adjunct to the physical examination.