In immersion oil preparation, which is used to diagnose parasitic skin infections such as scabies or lice infestation, a specimen of the suspected parasite is obtained and then viewed under a microscope.

Purpose of the Immersion Oil Preparation

  • To determine whether a skin disorder marked by itching is caused by parasites that live on the surface of the skin, such as lice or the mites that cause scabies

Who Performs Immersion Oil Preparation

  • A physician

Special Concerns about Immersion Oil Preparation

  • If the test is performed on a lesion that contains no parasites, a false-negative result is possible. In scabies, for example, only a small proportion of sores actually contain mites.

Before the Immersion Oil Preparation

  • No special preparation is needed.

What You Experience during Immersion Oil Preparation

  • If scabies is suspected, the doctor pours a drop of immersion oil on one of your sores and then uses a scalpel to scrape out the lesion. The immersion oil helps the mite stick to the scalpel blade.
  • If a lice infestation is suspected, the doctor locates the lice with a magnifying glass and then picks them up using a forceps. The doctor may also obtain specimens of lice eggs by plucking or cutting the hairs to which they are attached.
  • The test takes about 1 to 2 minutes.

Risks and Complications of Immersion Oil Preparation

  • You may experience minor discomfort or pain if your skin is scraped.

After the Immersion Oil Preparation

  • You may resume your normal activities.

Results of Immersion Oil Preparation

  • The specimen is usually examined right at the doctor’s office. If microscopic inspection identifies a specific parasite, appropriate medications will be initiated.
  • If no parasite is found but scabies is still suspected, your doctor may prescribe a trial of antiscabies therapy.


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: 11 Jan 2012

Last Modified: 27 Feb 2015