Bronchial asthma (BA), atopic dermatitis (AD) and allergic rhinitis (AR) are common atopic disorders with complicated etiologies. The atopic march from early AD to BA, AR, or both later in life and the extensive comorbidity among them indicates, that these atopic disorders might share a common mechanism (1). Moreover, heritability of these atopic disorders is high, being 35-95% for BA, 71-84% for AD, 33-91% for AR and 34-68% for allergen-specific serum immunoglobulin E (IgE) levels (1,2). Filaggrin is now considered as a major predisposing gene for many atopic disorders, which result in a major paradigm in dermatology and allergy research (3). Many studies pointed out an association of the filaggrin gene with different atopic disorders. More specifically, loss-of-function mutations in the filaggrin gene have been reported to have an association with various atopic/allergic disorders (3). Batchelor et al., reported that there is a strong and consistent association between filaggrin mutations and development of AD (4), but Summary Bronchial asthma (BA), atopic dermatitis (AD), and allergic rhinitis (AR) are well known atopic disorders with complex etiologies. This study was undertaken to investigate the role of filaggrin, eosinophil major basic protein (MBP) and leukotriene B4 (LTB4) in patients with BA, AD, and AR. Sera from 1,246 patients with different atopic disorders and 410 normal healthy controls were collected and were evaluated for filaggrin, MBP and LTB4 by specific sandwich ELISAs, whereas immunoglobulin E (IgE) was used as a positive control for atopic patients. Serum analysis showed that filaggrin levels were remarkably high in patients with AD and in patients with multiple (mixed) atopic disorders (p < 0.001), whereas its levels in BA and AR patients were low but much higher than in normal human sera (p < 0.01). MBP levels were also high in AR, BA and mixed atopic patients, whereas AD patients showed no increase of MBP (p > 0.05). In contrast, LTB4 level was found to be significantly low in all tested atopic patients groups as compared to the levels of LTB4 present in normal human sera (p < 0.001). In conclusion, these findings support an association between filaggrin, MBP or LTB4 and atopic disorders. Our data strongly suggest that filaggrin, MBP or LTB4 might be useful in elucidating the mechanisms involved in the pathogenesis of these atopic disorders.