BackgroundAllergic rhinitis, asthma, and Hymenoptera sensitivity affect approximately 20%, 9%, and 0.66% to 3.3% of adults in the United States, respectively. Various environmental control measures and pharmacologic options are available for symptomatic treatment of allergic rhinitis and allergic asthma. However, allergen‐specific immunotherapy is the only form of treatment that alters the natural history of allergic disease.MethodsA literature review was performed. Information from systematic reviews, meta‐analyses, and practice parameters were closely examined and summarized, and they are included in this primer.ResultsThere is evidence that supports the use of subcutaneous immunotherapy (SCIT) for the treatment of perennial and seasonal allergic rhinitis, asthma, and Hymenoptera sensitivity. Efficacy of SCIT has been established in the adult and pediatric populations. Adverse reactions occur in up to 71% of patients. However, the rate of serious or fatal side effects is very rare.ConclusionSCIT is safe and effective in the treatment of allergic rhinitis, allergic asthma, and Hymenoptera sensitivity. Adverse reactions occur but, in general, SCIT is well tolerated, and the vast majority of reactions are mild and very rarely fatal.