In tzanck smear, which is used to determine whether skin lesions are caused by a herpes virus, a blister is scraped and its contents are smeared on a slide. The slide is then stained and viewed under a microscope.

Purpose of the Tzanck Smear

  • To diagnose infections caused by herpes viruses, including herpes simplex (which causes fever blisters, cold sores, and genital sores) and varicella-zoster virus (responsible for chickenpox and shingles)

Who Performs Tzanck Smear

  • A doctor

Special Concerns about Tzanck Smear

  • A positive result only indicates the presence of herpes simplex (which causes fever blisters) or herpes zoster (which causes chickenpox and shingles), but does not distinguish between the two.

Before the Tzanck Smear

  • No special preparation is necessary.

What You Experience during Tzanck Smear

  • The doctor scrapes a sore and spreads the contents on a slide. You will experience minor discomfort while the sample is being collected.

Risks and Complications of Tzanck Smear

  • None

After the Tzanck Smear

  • You may resume your normal activities.

Results of Tzanck Smear

  • The specimen slide is colored with a special dye and examined under a microscope, either at the doctor’s office or at a pathology laboratory. The examiner looks for abnormally large cells (called giant cells) that are characteristic of herpes virus infections.
  • If the characteristic giant cells are observed upon microscopic examination, your doctor will institute appropriate antiviral therapy.
  • If results are negative, a viral culture may be ordered in an effort to detect the herpes virus, or your doctor may conclude that you do not have a herpes infec-


The Johns Hopkins Consumer Guide to Medical Tests

Simeon Margolis, M.D., Ph.D., Medical Editor

Updated by Remedy Health Media

Publication Review By: the Editorial Staff at

Published: 25 Jan 2012

Last Modified: 21 Jan 2015