Original article Epidemiology of allergic occupational diseases induced by Tetranychus urticae in greenhouse and open-field farmers living in a temperate climate area Background: The role of Tetranychus urticae (TU) as an occupational allergen has thus far been investigated only in selected farmer samples. Methods: The prevalence of TU-induced sensitization and occupational diseases in a randomized sample of farmers living in a temperate climate area was investigated. Occupational/nonoccupational symptoms, skin prick test (SPT) results with common allergens and TU, specific occupational test results, and greenhouse or open-field sources of TU exposure were assessed. The study design was cross-sectional. Results: The prevalence of positive SPT to TU was 6%. TU-induced allergic/ nonallergic complaints accounted for 65% of farmers with challenge-confirmed occupational disease. In all farmers, sensitization to common allergens was a risk factor for both current occupational and nonoccupational complaints, while TU sensitization was a prominent risk factor for occupational complaints. Furthermore, in SPT-positive farmers, only the presence of seasonal occupa- tional complaints was significantly associated with TU sensitization. Common allergen sensitization was a risk factor for development of TU sensitization, which was more frequent in greenhouse than in open-field workers. Conclusions: TU was a common nontraumatic, allergic occupational hazard for farmers. Since occupational seasonal symptoms could be directly related to the presence of TU sensitization, allergy to this mite should be routinely investigated in farmers. C. Astarita 1,2,6 , D. Gargano 1 , F. Manguso 3 , C. Romano 1 , D. Montanaro 1 , F. Pezzuto 4 , S. Bonini 2,5 , P. Altucci 1,2, , G. Abbate 2 1 Section of Allergology and Clinical Immunology, Division of Internal Medicine, ‘‘Flaviano Magrassi’’ Department of Clinical and Experimental Medicine, and 2 Postgraduate School in Allergology and Clinical Immunology, Second University of Naples Medical School, Naples; 3 Graduate Program in Digestive and Nutritional Physiopathology, ‘‘Federico II’’ University Medical School, Naples; 4 Allergology Unit, ASL SA 2, Salerno; 5 Allergology and Clinical Immunology, Second University of Naples Medical School, Naples, and Institute of Experimental Medicine, National Research Council (CNR), Rome; 6 Interdepartmental Research Centre ‘‘Ambiente e Salute’’, Naples, Italy Key words: allergic diseases; epidemiology; farmworkers; occupational allergy; Tetranychus urticae. Corrado Astarita, MD Via Vittorio Veneto, 3 80067 Sorrento Naples Italy Accepted for publication 6 August 2001 Tetranychus urticae (TU) is a macroscopic (0.5–1 mm), phytophagous mite, commonly known as red spider mite, which is ubiquitous in warm regions, infesting many vegetables and ornamental flowers cultured in open fields or greenhouses, as well as other plants and fruit trees in the summer–autumn period (1). We have already described seasonal occupational rhinitis in farm workers, mainly associated with asthma and/or contact urticaria, and an isolated hand-localized recurrent dermatitis, which proved to be allergic occupational complaints provoked by TU (1, 2). These clinical data, along with the role of this mite as a prominent occu- pational allergen, have also been confirmed in allergic greenhouse workers (3, 4) and in apple-cultivating farm- ers in a subtropical climate (5). Moreover, TU has been found to be an important allergen also in asthmatic nonfarmers with symptoms in the summer and autumn (6). The occurrence of allergic sensitization and related diseases in farmworkers is quite frequent (7, 8), although it is lower in farming environments than in cities and white-collar workers (9, 10). Chronic bronchitis and hypersensitivity pneumonitis have also been frequently reported among farm workers (11, 12). Consequently, a diagnosis of TU-induced allergy might be confused by the potential causative role of other allergens in inducing symptoms in these workers. Moreover, the prevalence of TU-induced, IgE-mediated sensitization or clinical allergy was recently investigated only in apple-cultivating farmers at subtropical climate (5) or in selected greenhouse workers, but not yet in a Allergy 2001: 56: 1157–1163 Printed in UK. All rights reserved Copyright # Munksgaard 2001 ALLERGY ISSN 0105-4538 1157