Allergy to Wasp stings
During the summer months insects of the order Hymenoptera which include the Yellow Jacket Wasps (Vespula germanica), HoneyBee (Apis mellifera) and Paper wasp (Polistes annularis) may sting unsuspecting people. If allergic to the stinging insect’s venom, these people might develop an allergic reaction, which may range from mild to life threatening. On average four Bee or Wasp sting anaphylaxis deaths are reported per year in the UK. You are therefore more likely to die in a Road Traffic Accident rushing to hospital than from the actual sting itself. Fire Ant allergy and anaphylaxis occurs in the USA but not in the UK.The most allergy provoking protein in a wasp sting venom is an enzyme called Antigen 5 (or Ves g V) whilst an enzyme called phospholipase (Api m II) is the major allergy provoking component of Bee venom. Sensitisation to insect venom can occur after a single sting. Other enzymes in insect venom called hyaluronidases may result in occasional cross-reaction allergy, but the vast majority of people are allergic to either wasp or bee but not both.
Wasps and Bees are social insects and rarely attack people, but tend to sting if disturbed. In the UK, the vast majority of insect sting allergic reactions are due to wasps. Bee sting allergy tends to occur in high-risk groups such as beekeepers, gardeners and farmers. Once stung the identifying feature of a bee sting is the stinger left behind in the skin, a wasp does not do this. The female honeybee carries the stinger and dies shortly after discharging a sting.
Diagnosis of Wasp and Bee Venom Allergy
We usually test for Wasp and Bee Venom allergy using the UniCAP RAST blood test that measures specific Venom IgE antibodies in the blood. The test has certain drawbacks in that it is difficult to predict severity of future reactions from the blood test. High levels of venom specific IgE do not necessarily predict a severe reaction. Occasionally venom allergic people have negative RAST tests – possibly due to their reacting to another protein component of the venom. Skin Prick Tests are more accurate for the diagnosis of insect venom allergy, but do carry a small risk of inducing a severe allergic reaction as traces of the venom are applied to the skin during testing. 10% of patients who experience wasp anaphylaxis will have negative allergy tests - possibly due to the IgE being tissue bound or there being a non-IgE mechanism. Hence a negative allergy test does not exclude sting anaphylaxis.Features of sting allergy.
Normally some pain redness and swelling accompanies a sting, this is not an allergy but rather a local toxic reaction to the venom. This non-allergic reaction develops over a period of a few hours with no adverse consequences and settles over a day or two.An insect venom allergic individual will have a more immediate and severe reaction. This may range from a mild reaction with redness and swelling spanning two joints, intense itching and pain all occurring within minutes of the sting. More severe reactions include generalised swelling and itching, urticaria and angioedema, faintness, sweating, a pounding headache, stomach cramps and vomiting, a feeling of "impending doom", a tight chest or choking sensation with swelling of the throat and in extreme cases, anaphylactic shock with death ensuing.
This may develop within 10 minutes of a sting, so early intervention is essential. There is no predicting whether future stings will result in more or less severe allergic reactions or anaphylaxis. However, if a long time has lapsed since last stung, the reaction is likely to be less severe.
