Doctors' Newsletter - Autumn 2008 - Douglass Hanly Moir Pathology

Allergy to Stinging Insects
Systemic or generalised reactions
• Should be treated, like other
forms of anaphylaxis, with
adrenaline and iv fluids. Rapidacting
antihistamines, steroids
and H2-antihistamines are often
used.
• iv glucagon may be needed for
refractory patients or those on
beta blockers.
• Local measures should include
sting removal and ice
compresses. Some authors
recommend use of a tourniquet.
• Appropriate observation in a
supervised environment (e.g.
emergency department) for
several hours is usual. Further
antihistamines and oral steroids
may be needed over the next
24-48 hours.
• Antibiotics may be needed after
wasp stings.
What management
is appropriate after a
significant sting
Follow up testing, first aid measures
and consideration of desensitisation
should be reviewed after significant
stings. Mastocytosis should
always be excluded by testing
for Tryptase. Patients should be
given advice on handling “a nexttime
situation”. This may include
access to injectable adrenaline such
as Epi-Pen or Epi-Pen Jnr plus other
medications suitable for use in such
a setting.
Patients must not be
prescribed beta blockers.
Anaphylaxis action plans and
current contact details of Allergy
Specialists are available online at
www.allergy.org.au.
How can I confirm my
patient has stinging
insect allergy
Specific IgE antibodies to bee
venom, wasp venom and other
stinging insects may be detected by
in-vitro assays (RAST or ELISA tests)
on serum.
Specimens for these tests should
not be collected within one week
of a sting that caused a significant
reaction, as the levels may be
depressed following consumption of
the allergen-specific IgE antibodies
after the sting. Note that the actual
level of specific IgE antibodies to bee
venom may not correlate very closely
with the severity of the reactions
experienced by the patient.
A very small number of patients may
have negative in-vitro tests for insect
venom allergy but positive skin tests.
If your patient has a very definite
history of venom allergy but negative
in-vitro tests, further discussion with
your immunologist is recommended.
Some of these patients may have
IgG4 antibodies directed to bee
venom. Skin tests with insect venom
are another diagnostic option but
carry some risk of generalised
reactions. Tests for a range of ant
venoms are available. Jumper
ant venom tests are not routinely
available but have been performed in
a research laboratory environment.
Sometimes it is not clear that the
patient did, in fact, have a bite or a
sting and in-vitro tests can provide
strong circumstantial evidence that
this was the case!
Apart from first aid or
next-time strategy, what
else should I advise my
patients
Insect avoidance measures should
be stressed, including:
• Care with outdoor activities
• Use of covered footwear
• Avoidance of clothing with bright
colours or floral patterns
• Avoidance of scents. (This is
particularly appropriate for
bee-venom sensitive patients.)
• When patients eat outdoors, some
caution should be exercised with
food or beverages that have fruity
scents. Having a means to wash
hands and face is also important.
• When gardening, gloves and long
trousers may provide additional
protection.
Products with activity against flies
and mosquitoes have little value in
discouraging bees, wasps or ants.
Sprays that have activity against
wasps and bees are not suitable for
personal application.
When is venom
immunotherapy
indicated
Immunotherapy is indicated for
patients with a systemic reaction,
although there are certain issues
to consider. These include safety,
efficacy, relative risk of re-sting
vs risk of immunotherapy, cost,
convenience, as well as patient and
doctor preferences.
The risk of a second systemic
reaction in adults has been estimated
at 60-70%. In children this may be
10-20% if their initial reaction was
milder.
Immunotherapy is not indicated for
large local reactions, although most
have demonstrable venom-specific
IgE on RAST or skin prick tests.
Varying practices exist for venom
immunotherapy in regards to the
reagents, the regime, duration and
monitoring of therapy.
Initial Evaluation Tests
IgE
Specific
IgE
(RAST)
TRYPTASE
Bee Venom I1
Paper Wasp Venom I4
Yellow Jacket Venom I3
If you have any enquiries, please contact Dr Karl Baumgart on (02) 98 555 286
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