Gender differences in asthma incidence, prevalence and clinical phenotypes have been extensively re-ported worldwide. A number of studies have shown that respiratory allergy, and especially asthma, is prevalent in males during childhood, whereas it becomes more frequent and severe in females between adolescence and adulthood, suggesting that sex hormones play a role as important modulators of immune response. The mechanisms underly-ing these differences between females and males are most likely the effects on the immune and inflammatory responses of female hormones and the result of the activity of various cells and cytokines. Understanding gender differences in respiratory allergies and asthma is important for providing effective education and personalized management plans for patients throughout their lives.