Lepromin skin test

A sample of inactive (cannot cause infection) leprosy-causing bacteria is injected just under the skin, often on the forearm, so that a small lump pushes the skin up. The lump indicates that the antigen has been injected at the correct depth.

The injection site is labeled and examined after 3 days, and again 28 days after the injection to see if there is a reaction.

People with dermatitis or other skin irritations should have the test performed on an unaffected part of the body.

If your child is to have this test performed, it may be helpful to explain how the test will feel and even demonstrate on a doll. Explain the reason for the test. Knowing the "how and why" may reduce the anxiety your child feels.

When the antigen is injected, there may be a slight stinging or burning. There may also be mild itching at the injection site afterward.

Leprosy is a long-term (chronic) and potentially disfiguring infection if left untreated. It is caused by Mycobacterium leprae bacteria.

This test is a research tool that helps classify the different types of leprosy. It is not recommended as the main method to diagnose leprosy.

People who don't have leprosy will have little or no skin reaction to the antigen. People with a particular type of leprosy, called lepromatous leprosy, will also have no skin reaction to the antigen.

A positive skin reaction may be seen in people with specific forms of leprosy, such as tuberculoid and borderline tuberculoid leprosy. People with lepromatous leprosy will not have a positive skin reaction.

There is a very small risk of an allergic reaction, which may include itching and, rarely, hives.

Leprosy skin test; Hansen disease - skin test

Dupnik K. Leprosy (Mycobacterium leprae). In: Blaser MJ, Cohen JI, Holland SM, et al, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 10th ed. Philadelphia, PA: Elsevier; 2026:chap 256.

James WD. Bacterial infections. In: James WD, ed. Andrews' Diseases of the Skin. 14th ed. Philadelphia, PA: Elsevier; 2026:chap 12.

Updated by: Jatin M. Vyas, MD, PhD, Roy and Diana Vagelos Professor in Medicine, Columbia University Vagelos College of Physicians and Surgeons, Division of Infectious Diseases, Department of Medicine, New York, NY. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.