Diagnosis is critical for appropriate therapies. Diagnostic strategies that confirm the diagnosis are somewhat problematic. Objectives: To investigate the in virto response to specific allergen stimulation and to compare allergen induced IL4 levels in allergic and control subjects. Methodology: This is a case control study involved two groups, date palm pollen allergic patient group and healthy controls. Skin prick test was performed, peripheral blood mononuclear cells were separated and cultivated in the presence and absence of date palm pollen. Levels of IL4 supernatant fluid and total serum IgE were measured by ELISA. Results: After specific allergen stimulation, the levels of IL4 were significantly increased in the patient group up to (67.8 pg). IL4 induced levels in patient group was markedly elevated than in control group (67.8 Vs 1.9). Conclusion: Allergen induced IL4 could give an extra evidence that confirm allergic rhinitis.