Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
per-prūrisco, ĕre, v. inch. n., to itch all over: ubi perpruriscamus usque ex unguiculis, Plaut. Stich. 5, 5, 20; App. M. 10, p. 209, 12.