photo-patch test

[fō′tō-păch]
n.
  1. A test for contact photosensitization in which a patch containing the suspected sensitizer is applied to the skin for 48 hours; if there is no reaction, the area is exposed to a reddening dose of ultraviolet light; if the reaction is then positive, a more severe reaction develops at the patch site than in surrounding skin.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.