Interleukin 5 (IL-5) has an enhancing effect on IL-4 induced immunoglobulin E (IgE) synthesis. Furthermore, IL-5 plays an important role in the differentiation, recruitment, activation and survival of eosinophils. IL-10 has a downmodulating effect on interferon gamma (IFN-gamma) production and can exert strong anti-inflammatory activities. Therefore, we analysed whether differences were present in IL-5 and IL-10 mRNA expression and protein production between T cells of children with allergic and non-allergic asthma, atopic dermatitis and healthy control children. We demonstrated significant increases in IL-5 mRNA expression and protein production in different T cell fractions of children with allergic and non-allergic asthma and children with atopic dermatitis as compared to healthy controls. This indicates that IL-5 is not only involved in allergy, but also plays a role in the inflammatory process of non-allergic asthma. Interestingly, IL-10 mRNA expression by purified T cells of children with allergic and non-allergic asthma and children with atopic dermatitis was strongly decreased as compared with that of healthy controls. In the peripheral blood mononuclear cell (PBMC) fraction, IL-10 mRNA expression was comparable between the four groups. We hypothesize that this decreased T cell derived IL-10 expression results in a lack of immunosuppression of the inflammatory process in these diseases. However, a role of monocyte derived IL-10 cannot be ruled out.