Sublingual immunotherapy (SLIT) is recommended in South Africa for the treatment of allergic rhinitis (with or without asthma) to house dust mites or grass pollens. Recent local studies have confirmed efficacy and safety but have also shown heterogeneity in clinical responses to the European SLIT vaccines used in the region. It has been found that regular follow-up with standardized rhinitis quality-of-life questionnaires improves compliance and encourages the patients to complete the 3-year SLIT course. Patients who discontinue usually do so in the first year because of logistic and financial reasons rather than adverse side effects. Further studies are in progress at the Allergy Diagnostic & Clinical Research Unit to identify immunologic markers of the SLIT responder phenotype.