**7. Skin reactivity tests**

The histoplasmin skin test reagent has been essential in defining the endemic area for *H*. *capsulatum* and can be used to evaluate previous exposure or latency but not active infection. It was useful in revealing the high frequency of asymptomatic infections in endemic areas.

The skin test has not been useful for diagnosis because it cross-reacts with other fungi (especially *Blastomyces dermatitidis*), produces interference with complement fixation antibody tests, and is insensitive to disseminated infection.

The skin test reagents are no longer commercially available.
