|Honey Bee Sting Allergy
by Eric Mussen
Renewed interest in honey bee sting allergy has surfaced as beekeepers approach their local agencies with requests to remove prohibitions, or become more lenient, with beekeeping, especially in urban and suburban settings. Eventually, the discussions focus on the topics of liability. Who will be responsible if problems develop and who will intercede in mitigating the problem?
The most difficult topic is human allergies to honey bee stings. What is the definition of allergy, for this purpose? What percentage of the population is allergic to honey bee venom? Can anything be done to alleviate such allergies?
Dr. David B.K. Golden (MD) has been studying this topic for many years. He combined his results with the results of 51 other studies to write a summary paper, “Advances in Diagnosis and Management of Insect Sting Allergy,” published in the Annals of Allergy, Asthma, and Immunology 111 (2013): 84-89. 7 Dr. Golden’s first topic is determining how many people actually are allergic. As a generality, 5 percent of our population is allergic to honey bee venom. However, how they respond to stings varies. We think of allergic response as anaphylaxis, leading to inability to breathe and possible death. The statistics demonstrate 1 percent of children and 3 percent of adults have endured such reactions. Another 5 percent or more have endured a “large local reaction,” with abnormally large and often persistent swelling around the sting site. Skin tests of adults have demonstrated that 20 percent will test positive to honey bee venom, rising to 30-40 percent in the weeks following a sting. But, if no systemic symptoms develop, most people lose the positive skin test in a few years. Those who still show a positive test are about 15 percent likely to have a systemic reaction with the next sting. However, while having the immunoglobulin E (antibody IgE) is necessary to have an anaphylactic response to bee venom, its presence alone is not sufficient to predict an anaphylactic reaction.
Trying to test for honey bee allergy is fraught with difficulties. In experiments with challenge stings, 40 percent of folks who already had suffered severe reactions had a subsequent one. Systemic reactions occurred with 23 percent of those who had moderate systemic reactions previously. Only 17 percent of those with cutaneous reactions developed more severe reactions. Although we have been told that wasp venom is cross-reacting among species, tests suggest that there are two different types of wasp venom. A negative test to one type does not mean that the other will test the same.
Skin tests do have a degree of value in predicting reactions to bee stings. The most sensitive patients are more likely to have stronger reactions. Those barely responding to prick tests are least likely to have major sting problems. However, there is enough variation in true responses to stings to suggest that the skin reactions are not truly reliable indicators of things to come. Up to 30 percent of patients who already had systemic reactions test negative in prick tests. But, half of those patients do test positive for venom-specific IgE in their blood. The remaining 15 percent give no physiologic clues that they still remain very susceptible, and about six percent of them do have subsequent anaphylactic responses.
Two newer tests are being studied. Basophil activation tests can be run on the patient’s blood cells. If the patient is allergic, either the basophils release a mediator of an allergic response or activation markers for a number of “clinically significant outcomes.” The second approach is even more complicated: using recombinant venom allergens to determine if the reaction is due to bee and/or wasp venom. It is thought that the cross reaction to both venoms is due to “cross- reacting carbohydrate determinants,” but that has yet to be proven. The wasp venom components are predictable. There is considerable variation in the bee venom component.
The final conclusion is that if someone had a previous severe reaction, it is likely (70 percent in adults; 30 percent in children) to happen, again, even 10-20 years later. Interestingly, these patients share another measureable trait. Their baseline serum tryptase levels make them more likely to: 1) have a severe reaction following a sting or from use of bee venom to try to desensitize them, or 2) not get the expected results (failure) from venom- immunotherapy (VIT). An elevated tryptase baseline occurs in about 10 percent of patients who respond severely to stings. It occurs in 25 percent of those whose blood pressure drops when stung. Normally, an elevated baseline suggests underlying mast cell problems, such as mastocytosis.
The paper finishes with an in depth discussion of the use of venom immune therapy (VIT) to desensitize patients. It discusses screening patients to determine when the treatment is appropriate. It describes details of doses and shot regimens: standard (15-20 weeks); modified rush (6-8 week); rush (2-3 days); and ultrarush (3-6 hours). The information covers the use of various medications with VIT, how long to maintain the shot routines, and when to stop getting the shots – can be up to a lifetime, but more often 5 years or less.
This is likely more information than you would ever need to know for an interview, but it is nice to have the facts. The paper can be found at: http://dx.doi.org/10.1016/j.anai.2013.05.026 .