A number of insects can either bite or sting and cause reactions in humans. Serious reactions that require a medical evaluation are almost always due to an insect sting. The “biting insects” such as bed bugs, mosquitoes, black flies and deer flies cause local reactions that are believed to be due to insect saliva. Reactions to biting insects can at times be very disabling but they rarely cause severe or life threatening reactions.
What kinds of insects sting?
There are four major classes of insects that can sting: the bees (honey and bumble bees), the wasps (paper and mud wasps), the vespids (yellow jackets, white faced hornets, yellow hornets) and the ants (fire ants).
All stinging insects have a stinger on the end of their abdomen and when agitated or threatened will land on your skin and insert a stinger into your skin. The stinger is attached to a venom sack which contracts and discharges a variable amount of venom into your skin depending on how long the stinger is in place.
The type of reaction is either local, meaning it happens in one place on the body or systemic, where the reaction occurs over the entire body. Local and systemic reactions are both excessive reactions of the immune system; they differ in the nature of the immune reaction involved. When an insect stings cause anaphylaxis, a small amount of the venom protein interacts with your mast cells and basophiles and cause them to release substances that produce the allergic reaction.
Local reactions usually start with a burning, itchy swelling that occurs within minutes of the sting. Delayed swelling can occur (usually 12-24 hours after the sting) and sometimes be disabling. Local reactions are not dangerous reactions and are usually treated with antihistamines and local application of ice packs. More severe local reactions may require intensive medical treatment.
With few exceptions these types of reactions occur within an hour of the sting. Severe systemic reactions can be associated with almost no local reaction and sometimes the person is not even aware of being stung!
Symptoms of a systemic reaction include dizziness and light headedness (due to a drop in blood pressure) sometimes progressing to loss of consciousness, flushing of the skin and hives over the entire body, swelling of the throat with difficulty swallowing, wheezing, chest tightness and shortness of breath. These reactions are a medical emergency and need immediate attention. The most severe phase of a systemic reaction occurs in the first hour and if promptly treated severe symptoms do not usually recur after that.
If you think you may have an insect sting allergy, you should make an appointment with one of the allergists at Tufts Medical Center. We use a skin test to determine which insect venoms might be causing your allergic reaction. If you have been stung by one insect, you may be also reactive to other insect venoms because they share some common allergens. If you have had systemic reactions, you are potentially vulnerable to any venom to which you show a positive skin test.
The doctors in the Division of Allergy at Tufts Medical Center have expertise in treating sting reactions. Some of the treatments that our doctors provide include:
Our doctors can provide you with tips on how to help prevent yourself from being stung. These tips include avoiding digging in the ground especially in unfamiliar areas. Off trail hiking is also somewhat hazardous. During a picnic you should avoid spending time around food that is attracting yellow jackets. You should also try to look for nests of yellow jackets and wasps on the sides of houses and on trees and have a professional remove them.
Treatment of a sting reaction
If you have a history of systemic reactions to insect stings you should have medication always available in high-risk situations, especially during warm times of the year. Our doctors will usually prescribe you with medication that consists of an adrenaline injector such as EpiPen and rapidly acting antihistamine such as Benadryl.
If you think you are starting to have a systemic reaction, you should take rapidly acting Benadryl. Early systemic reactions are often first evident by a feeling of dizziness, flushing, tingling of the lips or hands, itching in the throat, chest tightness or shortness of breath. If you are dizzy or short of breath or having difficulty swallowing, then the best thing is to give yourself a shot of adrenaline in the front of the thigh. It is always best to head for a hospital if a reaction is in progress, just in case it worsens.
Desensitization is a procedure that involves giving you shots over a period of time in gradually increasing dosage to make you less sensitive to insect venoms. Medical trials show that desensitization is effective and will prevent serious reactions in the majority of people. It requires gradually increasing doses at weekly intervals for approximately 12 weeks followed by maintenance doses at monthly or longer intervals. Maintenance doses are usually kept up for 3 to 5 years and then they usually can be stopped.
Studies indicate that severe sensitivity rarely recurs after a course of desensitization. We often recommend desensitization if you are commonly in high-risk situations or if you frequent areas in the summer time where medical attention is not readily available. The pros and cons of this therapy will be discussed with you.
To make an appointment for an insect sensitivity related issue, please call 617-636-5333.