Background and aims Psoriasis is a TH1 and TH17 cells–dependent autoimmune disease of the skin and joint while allergic disorders are TH2 cell-dependent. There are conflicting reports about the effect of atopy on psoriasis. With regard to these reports, the aim of the current study was to determine the frequency of atopy, allergic disorder (such as allergic rhinitis, asthma and eczema) and eosinophilia in patients with psoriasis

Methods For this purpose, this case-control study was performed in Mashhad Ghaem hospital. History of allergic diseases including: allergic rhinitis, asthma and eczema were evaluated based on ISAAC standard questionire. Skin prick test was performed with 5 common aeroallen in our reigeon and atopy was define as a result of only one positive skin prick test.Also peripheral blood samples were obtained to determine serum levels of IgE and blood eosinophil cell count in both study groups.

Results A total of 52 patients with psoriasis,and 50 healthy subjects as the control group were considered. Between allergic diseases only asthma was lower in psoriatic patients rather than controlbased on ISAAC questionarie(p=0.044). There is no significant diffrence between result of skin prick test (atopy) in case and control group(p). Also no significant correlation was found between eosinophil count (p=0.057) and Ig E level in case and control group (p=0.88).

Conclusions In general, these findings suggest that the Asthma was not common in psoriasis, and support the concept that Asthma protects against the autoimmune disease such as psoriasis.