Refaat MM, et al. - In this case-control study involving 40 individuals, researchers evaluated the role of serum level diamine oxidase (DAO) enzyme as a diagnostic marker in respiratory allergy. Participants in the study were patients with respiratory allergies (atopic asthma and allergic rhinitis) as well as 40 age- and gender-matched controls. A detailed past history of allergy has been gathered from each candidate including a family history of allergy. According to the findings, patients had higher levels of DAO than controls. A positive relationship was found between severity of disease and DAO. There was no significant link between DAO level and age, type of respiratory allergy, duration of disease, pulmonary function test, eosinophilia, and total IgE. DAO had high sensitivity and high negative predictive value. Findings suggested that DAO can be helpful in evaluating the severity and eliminating the respiratory allergy.