Among Gamasina (Acari: Mesostigmata) mites, some dermanyssoid species are known to cause gamasoidosis, a human dermatitis characterized by papulosquamous eruptions and urticarian lesions. We describe a case of mite infestation which occurred in public conference halls in Ferrara (Italy), affecting four people who attended the place and showed signs of gamasoidosis. The mites were collected and characterized using scanning electron microscopy, light microscopy and mitochondrial DNA sequencing (Cytochrome c oxidase subunit I partial CDS). Based on morphological and molecular data, the species responsible for the infestation was identified as the special lineage L1 of the poultry red mite, Dermanyssus gallinae (De Geer) (Acarina: Dermanissydae), a cryptic species known to be associated with pigeons. Rock doves, Columba livia Gmelin (Columbiformes: Columbidae) were roosting on the top of the public building, thus the mites probably gained access to the halls through small window openings. The present case report is the first one providing morpho-molecular identification of a D. gallinae cryptic species responsible of gamasoidosis in Italy. •Mite infestations occurred in public conference halls in Northern Italy, causing gamasoidosis.•Morpho-molecular analyses identified Dermanyssus gallinae L1 as responsible for the infestation associated with rock doves.•This was the first morpho-molecular characterisation of human infestation by the cryptic species D. gallinae L1.