Information on the natural history of hypersensitivity reactions helps decide which patient urgently needs venom immunotherapy (VIT).

The frequency of self-reported systemic allergic reactions (SAR) to Hymenoptera stings is approximately 3–7% in the Northern Hemisphere. About 25% of SAR are severe (anaphylactic shock). Fatal sting reactions are infrequent. The most critical risk factor for severe insect sting anaphylaxis is mast cell disease. Other risk factors are higher age, vespid venom allergy (in contrast to honeybee venom allergy), repeated stings, male sex, and treatment with ACE inhibitors. Initial significant local reactions seem not to play a risk factor for subsequent SAR.

The majority of risk factors for severe anaphylaxis are not adjustable. For patients presenting with well-defined risk factors for very severe or even fatal anaphylaxis, VIT is of utmost importance, and they should be performed for the rest of their life. Sting challenge tests are required to identify patients in whom treatment was ineffective. Those patients, who did not receive VIT, although presenting with a firm indication, or VIT was stopped, require yearly monitoring to teach preventive measures and renew the emergency kit.