Histoplasmosis Skin Test

Norm of Histoplasmosis Skin Test

Negative as evidenced by no induration and erythema <5 mm in diameter.


Description of Histoplasmosis Skin Test

(See Histoplasmosis serology—Blood.) Skin tests become positive 2–3 weeks after infection and remain positive in 90% of the infected population for life.


Professional Considerations of Histoplasmosis Skin Test

Consent form NOT required.

  1. Travel history should be included as part of the client's health history to determine exposure to high-incidence endemic areas.
  2. Obtain an alcohol wipe, a needle, a syringe, and histoplasmin—an antigen prepared from culture (usually commercially prepared).



  1. Histoplasmin is injected intradermally.
  2. Record the location of the injection for reading.
  3. The injection should follow a blood draw for serum titer.


Postprocedure Care

  1. Read the test in 24–48 hours. An area of erythema and induration of >5-mm diameter is indicative of a positive reaction.


Client and Family Teaching

  1. See Histoplasmosis serology—Blood.


Factors That Affect Results

  1. Test may be falsely negative in 50% of people with disseminated histoplasmosis and 10% of people with cavitary histoplasmosis.
  2. False-negative results may occur because of depressed immunologic status (not in HIV clients) or steroid therapy.
  3. False-positive results may occur in people with blastomycosis (30%) or coccidioidomycosis (40%).


Other Data

  1. Acutely ill clients may not have a positive skin reaction.
  2. This test is not recommended because of the difficult interpretation and because it may cause the serology test to be falsely positive.