Introduction: Tetrameric Ig are produced and secreted by plasma cells. However, it is well documented that plasma cells also produce and secrete Ig-free light chains (FLC; and ). Recent studies in animal models for allergy suggest the existence of an IgE-independent hypersensitivity response involving antigen-induced mast cell activation, mediated by FLCs. In this study we aimed to explore the relation between serum FLC and IgE in various patients with high levels of specific IgE for food and respiratory allergens. Materials and Methods: 20 subjects with food allergy, 21 subjecs with respiratory allergy and 15 controls were selected and serum was collected for determination of kappa and lambda FLCs, total IgE and specific IgE. Total IgE, FLCs were determined by ELISA. Specific food and respiratory allergens was determined by Improvio C Blotting Methods. Results: The results show that FLC are significantly increased in patients with high allergen-specific IgE as detected by immunoblotting (for 30 food and 30 respiratory allergens). Among the food allergens, the highest specific IgE was detected for celery, carrot, cheese mix, and milk and spelt flour, Derm.farinae, Acarus siro, cockroach, mixed grasses and rye pollen for the respiratory allergens. Milk allergic subjects show significant higher increases in than FLCs, while in others -for example celery allergics- this augmentation was reverse. No significant association between and FLCs with others was seen. Conclusion: FLC subunits may be considered as unique markers for allergic sensitization. lklklk