This article is from the Children Allergies and Asthma FAQ, by Eileen Kupstas Soo firstname.lastname@example.org with numerous contributions by others.
Various insects can cause allergic reactions. Wasps, honey bees,
hornets, yellow jackets and ants are the insects most likely to cause
strong allergic reactions. Some biting insects (mosquitoes, flies,
lice, kissing bugs and fleas) can cause allergies as well because they
inject saliva to thin the blood when they bite. Finally, some
caterpillars are covered with hairs that contain a substance irritating
to human skin and this can sometimes cause allergic reactions.
In general there are three kinds of reactions to insect stings. The
first kind, normal reactions, involve pain, redness, swelling, itching,
and warmth at the site of the sting. The second kind, toxic reactions,
are the result of multiple stings. Five hundred stings within a short
time are considered likely to kill because of the quantity of venom
involved. As few as ten stings within a short time can cause serious
illness. Symptoms of toxic reactions include muscle cramps, headache,
fever, and drowsiness.
Allergic reactions are the third type. They may involve some of the
same symptoms as toxic reactions, but may be triggered by a single
sting or a minute amount of venom. Any non-local reaction to a single
sting should be considered allergic until proven otherwise.
Allergic reactions may be local or systemic. An allergic reaction is
considered local if it involves only the stung limb, regardless of the
amount of swelling. A slight systemic reaction may involve hives and
itching on areas of the body distant from the sting site as well as
feelings of anxiety and being run down. A moderate systemic reaction
may include any of the above plus at least two of edema (swelling),
sneezing, chest constriction, abdominal pain, dizziness, and nausea. A
severe systemic reaction has the symptoms already described plus at
least two of difficulty in swallowing, labored breathing, hoarseness,
thickened speech, weakness, confusion, and feelings of impending
The most serious symptoms are the closing of airways and shock
(anaphylaxis) since they can be fatal if not treated quickly and
effectively. Allergic reactions may begin within ten to twenty minutes
after the sting or they may be delayed. Usually, the sooner the
reaction starts, the more severe it will be.