Bees and wasps inject venom when they sting. When a person is stung by a bee or wasp, they typically have an intense, burning pain followed by erythema (redness) and oedema (swelling) at the site of the sting. This usually subsides within a few hours. After an initial sting, some people have an immune response and produce IgE antibodies. In these people, subsequent stings can trigger a rapid inflammatory response referred to as a 'type 1' hypersensitivity reaction.
Hypersensitivity reactions to bee or wasp venom can be local or systemic, can vary in severity, and are typically of rapid onset. Large local reactions are characterised by oedema, erythema and pruritus, cover more than 10 cm in diameter and peak at between 24 and 48 hours after the sting. Systemic reactions can be measured using the Mueller grading system. Severity ranges from grade 1 to grade 4. A grade 1 systemic reaction is characterised by generalised urticaria or erythema, itching, malaise or anxiety. Grade 2 reactions may include symptoms associated with grade 1 reactions, as well as generalised oedema, tightness in the chest, wheezing, abdominal pain, nausea and vomiting, and dizziness. Grade 3 reactions may include symptoms associated with grade 1 or 2 reactions, as well as symptoms of dyspnoea, dysarthria, hoarseness, weakness, confusion, and a feeling of impending doom. Grade 4 reactions may include symptoms associated with grade 1, 2 or 3 reactions, as well as loss of consciousness, incontinence of urine or faeces, or cyanosis.
Recently published guidelines for the treatment of bee and wasp venom allergy issued by the British Society for Allergy and Clinical Immunology classify systemic reactions as mild, moderate or severe. A mild systemic reaction is characterised by pruritus, urticaria, erythema, mild angio-oedema, rhinitis and conjunctivitis. Moderate systemic reactions may include mild asthma, moderate angio-oedema, abdominal pain, vomiting, diarrhoea and minor or transient hypotensive symptoms such as light-headedness and dizziness. Severe systemic reactions may include respiratory difficulty such as asthma or laryngeal oedema, hypotension, collapse or loss of consciousness, as well as double incontinence, seizures, or loss of colour vision. Anaphylaxis is defined by the European Resuscitation Council as a severe, life-threatening, generalised or systemic hypersensitivity reaction.
Data from the USA suggest that the prevalence of allergy to bee and wasp venom is between 0.4% and 3.3%. In the UK, insect stings are the second most frequent cause of anaphylaxis outside medical settings. It is estimated that of all deaths from anaphylaxis between 1992 and 2001 in the UK, approximately 62% were a result of reactions to wasp venom and approximately 9% were caused by reactions to bee venom. Some people who have a systemic reaction after being stung do not have another reaction when re-stung. It is estimated that after a large local reaction 5% to 15% of people go on to develop a systemic reaction when next stung. Approximately 14% to 20% of those who have a mild systemic reaction have another systemic reaction when next stung. For people who have experienced an anaphylactic reaction, the risk of having a recurrent episode is estimated to be between 60% and 70%.
The main method for diagnosing an allergy to bee and/or wasp venom is skin testing with venom. Another less sensitive method is measurement of allergen-specific IgE antibodies in serum. Clinicians may also measure serum tryptase at baseline (after a reaction to a sting has subsided) because this may predict the severity of a response to a subsequent sting.
Clinicians typically give an emergency kit to people with a venom allergy who are considered at risk of systemic reactions. The kit includes adrenaline (epinephrine; intramuscular injection) and can also include other emergency treatments such as a high-dose antihistamine (oral), a corticosteroid (inhaled), and/or a bronchodilator (inhaled). Preventive measures include advice on how to avoid bee and/or wasp stings.
In the UK, clinicians consider offering venom immunotherapy to people with a history of systemic allergic reactions to bee venom and/or wasp venom. Venom immunotherapy aims to reduce the risk of future systemic reactions and the severity of a systemic reaction when 1 occurs. People considered for venom immunotherapy are usually those who have had severe systemic reactions, or those who have experienced moderate systemic reactions and have additional risk factors, such as a high baseline serum tryptase or a high risk of future stings, or whose quality of life is significantly affected by venom allergy.