Severe allergic reactions to wasp or bee stings is not something that we see much of within a Paediatric Allergy Practice thankfully. Severe reactions to insect venom are rare and when they do happen, they are much more common in people who have been stung multiple times and in practice this usually means adults, most typically beekeepers or people who work in environments where they are much more likely to be stung. I do occasionally get consulted because of concern that a child may have had an allergic reaction to an insect sting although in many cases it will turn out that what they have in fact had is a normal local reaction to insect venom. This is not an allergic response but simply a sensitivity to the toxin that stings contain. One thing that is always worth bearing in mind when there is a concern about a possible allergic reaction to a sting is whether the child has ever been stung before. The way that our immune systems work requires that there must have been at least one exposure to the venom protein in question in the past before an allergic reaction can happen. With insect stings, the only possible way that exposure may have happened in the past would be a previous sting, so if this is the child’s first sting, it is extremely unlikely that any reaction would be allergic in nature. However, if it is not the first sting, then of course there is a possibility that there might be an allergic reaction. Interestingly, the genetics for atopy, which is the underlying genetic tendency to have allergic issues such as eczema, asthma, hay fever and food allergies, does not seem to carry an additional risk for venom allergy so when we do find patients who have genuine insect sting allergies, they are not typically children who have other allergic issues. Likewise, having a history of eczema, food allergies, asthma and hay fever does not put a particular child at an additional risk of being allergic to insect stings.
The first part of the assessment when there is a suspected sting allergy is a clear history as to what actually happened. Trying to identify and differentiate bees from wasps is difficult, although one of the most useful things to know is that bees will leave the sting in the skin whilst wasps don’t, so if there is a visible stinger left on the surface of the skin, then it must have been a bee. Typically, allergic reactions will happen within a few minutes and involve an itchy rash which occurs not only at the site of the sting but also at other sites, whereas a large local reaction which is not allergic in nature would just happen around the site of the sting itself. In my experience, most suspected allergic reactions will turn out simply to be non-allergic reactions and nothing to worry about. However, even if there is an allergic component, unless it was severe with anaphylactic features such as difficulty in breathing or collapse, then chances are a subsequent sting will also lead only to a mild reaction although of course it would make sense to have precautions in case of a more severe reaction. However, if the reaction was severe and did involve features of anaphylaxis, then it is important to discuss in detail the possibility of venom desensitisation. This is a course of injections that start with deliberate exposure to very small amounts of venom but gradually increasing amounts and will reduce the risk of a more severe reaction happening in the future. It is only suitable for those children who have had severe allergic reactions and may not be appropriate even for those who have, given the quite arduous nature of the treatment itself.
One of the most challenging features of trying to make a diagnosis of a venom allergy is that the testing is not straightforward. There are no reliable skin prick tests for bee or wasp venom so we have to do blood tests and unfortunately even with these, there are very commonly false positives. This can prove very unhelpful when there is an unclear story and lack of certainty about the diagnosis. It is therefore generally accepted that blood testing for insect venom allergy should only be done when a child is being assessed for desensitisation treatment. Essentially, this means that the test will confirm the presence of allergic antibodies to insect venom and guide which venom should be desensitised against when there is a very clear history of allergic reaction. The allergy test is not useful at differentiating children who came out in a rash after a sting into those who are allergic and those who are not. This can be very frustrating for both parents and doctor alike when we simply want a clear answer as to whether the child is allergic or not.
The good news for those who do suffer from venom allergies is that progression from mild to severe reactions is very rare, there are lots of steps that can be taken to minimise the risk of being stung again and also in those who are most at risk of severe reactions (those who have had a severe reaction before) have the option of desensitisation treatment which is extremely successful. There are many useful resources relating to venom allergy on the website of the Anaphylaxis Campaign.
