Abstract: Objective To investigate the etiology of papular urticaria: is it caused only by arthropod-like insects-bite allergy, or by multiple factors such as food allergy, disturbance of gastrointestinal function and infection? Methods We searched, by computer and manually, the foreign and domestic literature related to the etiology of papular urticaria published since 1950s, and according to the methods of evidence-based medicine, systematically evaluated the evidence supporting either the insect-bite theory or the multiple factor theory. Results Twenty-nine articles (22 English and 7 Chinese) supported the theory of hypersensitivity to bites from certain insects such as mosquitoes, gnats, fleas, mites, bedbugs etc. Two articles in Chinese mentioned the possibilities other than insect-bite, but the reliability was unconvincing, because the authors did not present the source of data or statistical methods used in the articles. The evidence from epidemiology, histopathology, laboratory and clinical researches all supported the insects-bite theory. No proven evidence was found supporting other aetiological hypotheses. Conclusion Our results suggest that papular urticaria is caused only by the allergy to stings or bites of arthropods, and other hypotheses still lack convincing evidence.

Key words: Papular urticaria, Arthropods, Insect bites and stings