Stinging Insect Allergy

We get many questions regarding allergic reactions to insects. Families are concerned about a wide array of insect bites and stings. We hear about a whole host of different type of reactions- immediate, delayed, local, and total body. What does the allergist have to offer regarding testing and guidance regarding these problems. My resource for what follows is the American Academy of Allergy, Asthma, and Immunology: Practice Parameter- Stinging insect hypersensitivity: A practice parameter update 2011.

Reactions to insect stings.

Reactions can be;

  • Local- limited to the area of the sting/bite-red, swollen, itchy, painful
  • Large Local- involves an area beyond the site-size increases over 1-2 days, the swelling is ~4 inches, lasts 5-10 days
  • Systemic reactions – mild or life-threatening
  • Delayed reactions
  • Toxic reactions

The systemic reactions are the ones that are more concerning. These reactions have a number of features that tell us something more serious is going on. These are the reactions that would require the attention of an allergist. The features of a systemic reaction may include;

  • Skin responses- diffues hives or swelling
  • Respiratory – cough and wheeze
  • Upper airway obstruction- where swelling of the airway (throat, tongue) caused breathing problems
  • Cardiovascular
  • Cardiac- heart rhythms, coronary artery spasms
  • Hypotension/shock
  • Gastrointestinal- nausea, vomiting, diarrhea, abdominal pain
  • Neurologic- seizures

 Who needs self-administered epinephrine (an Epi Pen)?

A patient with a history of a severe reaction should have injectible epinephrine prescribed.

Who should see an allergist?

Any patient who has had an allergic reaction and is in need of venom immunotherapy to prevent or lessen the impact of a subsequent allergic reaction. The allergist can perform testing for those who need to be on immunotherapy.

Testing is done on those who are candidates for the venom immunotherapy program.

  • Individuals who have had a systemic reaction (exclude hives in <16 years of age)
  • Individuals who have a systemic reaction and can go on the venom immunotherapy program

Criteria for immunotherapy- Allergy shots

There needs to be a history of a systemic reaction to an insect sting and the demonstration of IgE-antibodies by skin testing or by in vitro testing (blood testing).

Exception- Venom immunotherapy is not indicated for <16 years of age with only a skin reaction. Total body hives without any other organ system involvement would not be a reason to go on venom shots.

Venom immunotherapy is almost completely effective in preventing a life-threatening reaction to a sting.

The Venom Clinic at Riley Children’s Specialists at IU Health North

This clinic is intended for those children who have had a serious immediate systemic reaction to a sting and plan/need to go on venom immunotherapy. If the reaction was not a severe reaction there is no need to be seen in this clinic. If  there is no interest in going on immunotherapy or the logistics of the venom program makes it impossible, then there is no need to be scheduled. In this clinic we are testing to implement an immunotherapy treatment program.

What insects do we test for?

We have extract and treatment sets for the following;

  • Honey bee
  • Wasp
  • Yellow-faced hornets
  • White-faced hornets
  • Yellow Jackets

We call this grouping  ‘Hymenoptera’- I will use this term to separate those stinging insects that can be used for venom immunotherapy.

 What insects do we not test for allergic reactions?

 It would be easy to just refer to the list above. This list of ‘exceptions’ is significantly longer. However, we have concerned families who report reactions to a significant representation of the insect kingdom. Of note, some of these have a legacy. They were items that were tested in the past century. Those items have undergone scrutiny and are not approved.

  • Mosquitos
  • Flies
  • Spiders
  • Fleas
  • Bed bugs
  • Gnats
  • Fire ants (these are regional, they cause reactions)

When is the best time to test?

Allergy testing should not be done for at least 6 weeks after the event. Skin testing and blood testing may be non-reactive if testing is done too early.

How is allergy testing done?

Skin testing is performed on the 5 species of Hymenoptera. Insect identification is often difficult and unless the story is a perfect fit, all 5 are tested. Once, a professor who’s life’s work was with the wasp presented for an evaluation- he was certain that the culprit was a wasp. He was only tested to wasp. The concern is that if testing is limited to only one species, significant sensitization to one of the other species may be missed.

The tests are intradermal- a small needle is introduced into the skin. There are 4 concentrations that are used for testing. In the worse case-scenario- 5 species times 4 concentrations plus 2 control injections would be 22 intradermal injections.

Venom Immunotherapy

The treatment for a serious systemic reaction to ‘Hymenoptera’ is a long and involved program. If the program does not fit the constraints of time/travel, then the option is to practice avoidance and have the injectible epinephrine available. Allergy testing should not be performed if there is no interest or ability to undergo the immunotherapy program.

A venom immunotherapy program should be continued for 3-5 years. The build-up to a maintenance dose should be performed in the allergist’s office. This takes about 25 weeks to get to the top dose at a once per month injection interval. There is a mandatory 30 minute wait after the shot is given. This is how we do this in our office.

The venom immunotherapy program decreases the risk of a systemic reaction with an efficacy of 98%. Patients who have had a systemic reaction and have shown positive tests to these insects are advised to start venom immunotherapy. The purpose of the program is to prevent a life-threatening reaction with the secondary gain of decreased anxiety related to exposures.

 Conclusions

 The venom clinics are held on the 3rd Tuesday of every third month (March, June, September, and December). Those appointments are best for those children who have had qualifying systemic reactions and plan to go on allergen immunotherapy. The clinic is geared for doing the diagnostic testing.

For those who cannot for whatever reason go on a venom immunotherapy program, appointments can be made in our new patient opportunities. At these time we do not do testing.

If you are looking to make an appointment and you are not sure, please feel free to call.

FEL (August 2012)