Objective: Type I autoimmune response (autoallergic) and type IIb autoimmune response have been described in the pathogenesis of chronic spontaneous urticaria (CSU). However, the aetiology is still unknown. In this study, we aimed to investigate the frequency of atopy and the effects of atopy and allergen types on the course of the disease in patients with CSU.

Materials and Methods: The study included 261 CSU patients aged 18 years and older who underwent the aeroallergen skin prick test and/or serum-specific IgE test. Clinical and laboratory characteristics of the patients were compared according to the presence of atopy and the allergen types.

Results: According to aeroallergen-specific IgE, 89 patients (34.1%) were considered atopic. Female gender, thyroid autoantibody (TPO, Tg) positivity, and ANA positivity were significantly higher in the nonatopic group (p=0.002, p=0.001, p=0.008, respectively). Total IgE levels, and high total IgE and C4 level rates were higher in the atopic group (p<0.001, p<0.001, p = 0.02, respectively). High total IgE (3.92- fold risk, 95% CI) and elevated C4 (2.41-fold risk, 95% CI) were independent risk factors for atopy. There was a significant difference in C4 levels between pollen and multiple sensitization groups (p=0.007). No significant difference was found between the groups in terms of age, disease duration, presence of angioedema, sedimentation, CRP, C3 and antihistamine treatment response (p=0.13, p=0.80, p=0.68, p=0.12, p=0.93, p=0.28, p=0.58, respectively) .

Conclusion: The findings suggest a possible association between atopy and chronic spontaneous urticaria, and that atopy may predispose to chronic urticaria. Patients with CSU can be classified as atopic and nonatopic (autoimmune), and this classification may be effective in determining the step treatment modality.