What's eating you? Oak leaf itch mite (Pyemotes herfsi)

The oak leaf itch mite (Pyemotes herfsi), also known as the oak leaf gall itch mite or the itch mite, is a mite thought to have originated in Europe. Previously, the mite was reported to have caused a papular rash in grain workers in the Czech Republic.1 In late August 2004, the first reported cases of a dermatitis resulting from bites of this mite in the United States occurred in Kansas. The outbreak eventually affected more than 20,000 residents, prompting an investigation that led to the identification of P herfsi as the most likely responsible organism; these mites were found to be infesting nearby pin oak trees (Quercus palustris).2 Since then, cases have been reported in Illinois, Nebraska, Ohio, Oklahoma, Missouri, Tennessee, and Texas.3 We report a case involving the oak leaf itch mite in Lancaster, Pennsylvania, that caused a pruritic papular rash in a patient.