Human immunodeficiency virus (HIV) infection had been reported to increase serum Immunoglobulin E (IgE) and the prevalence of atopic diseases. However, there is a paucity of data in the literature on the association between the severity of HIV infection and serum IgE and atopic diseases among children in the Sub-Sahara African region, particularly Nigeria. OBJECTIVES: To assess serum IgE levels, prevalence and pattern of atopic diseases, and their association with the severity of HIV infection in children on antiretroviral therapy. METHODS: One hundred HIV-infected children on antiretroviral therapy recruited consecutively into a cross-sectional study were age and sex-matched with 100 non-infected. International study of asthma and allergy in childhood (ISAAC) proforma was used to obtain information from all the participants. Serum IgE levels and Cluster of differentiation (CD) 4+ counts of all the participants were determined, as well as, HIV viral load of the infected participants. HIV viral load, CD 4 counts and WHO clinical staging were used to classified HIV severity. Data analysis was done using statistical package for social sciences (SPSS) version 21, and statistic significant level was put at p<0.05. RESULTS: Mean (SD) serum IgE of the HIV-infected and non HIV-infected children were 150.6 (12.7)iμ/ml and 94.8 (5.6)iμ/ml respectively (p=0.001). The overall prevalence of atopic diseases among HIV-infected and non-infected children were 15.0% and 6.0% respectively, p=0.031. Among HIV-infected, allergic conjunctivitis accounted for 11.0% and allergic rhinitis 4.0%, while among non-infected allergic conjunctivitis, atopic dermatitis and asthma accounted for 4.0%, 1.0% and 1.0% respectively. Based on WHO clinical staging, serum IgE level was significantly higher in advanced disease than in early (p<0.001), and likewise the prevalence of atopic diseases (p=0.011).Funso Abidemi Olagunju et.al. Serum immunoglobulin E levels and atopic diseases in human immunodeficiency virus-infected and non-infected children and their association with the severity of HIV infection at a tertiary hospital, south-west Nigeria