Insect allergy

Insect Allergy
Prof. Dr. Saad S Al Ani
Senior Pediatric Consultant
Head of Pediatric Department
Khorfakkan hospital
Sharjah ,UAE
Saadsalani@yahoo.com

History
The first reports of stinging
insect allergy came from the
Middle East thousands of
years ago.
Even at that time, people
understood that a small insect,
such as a bee or a wasp, had the
potential to cause serious
illness or even death.
http://www.theonlineallergist.com
19 April 2013 2
Insect Allergy Prof. Dr. Saad S Al Ani
Khorfakkan Hospital ,Sharjah ,UAE

Introduction
Allergic responses to
stinging
1. Localized cutaneous
reactions
2. Systemic anaphylaxis
19 April 2013 3

Cont.
Allergic reactions that are caused
by inhalation of airborne
particles of insect origin result in:
1. Acute or 2.Chronic
respiratory symptoms of seasonal
or perennial:
i. Rhinitis
ii. Conjunctivitis
iii. Asthma
19 April 2013 4

Etiology
Most reactions to biting and
stinging insects, such as those
induced by mosquitoes, flies, and
fleas, are limited to a primary
lesion isolated to the area of the
bite and do not represent an
allergic response.
19 April 2013 5

Cont.
Occasionally, insect bites or stings
induce pronounced localized
reactions or systemic reactions
that may be based on:
1. Immediate
or
2. Delayed hypersensitivity
reactions.
19 April 2013 6

Cont.
Systemic allergic responses
to insects are attributed most
typically to immunoglobulin (Ig)E
antibody–mediated
responses, which are caused:
i. Primarily by stings from
venomous insects of the order
Hymenoptera
ii. More rarely from
ticks, spiders, and kissing bug.
19 April 2013 7

Cont.
Systemic reactions to
stinging insects occur in 0.4-
0.8% of children and 3% of
adults
19 April 2013 8

Cont.
Members of the order
Hymenoptera include:
i. Apids:
* Honeybee * Bumblebee
ii. Vespids
* Yellow jacket * Wasp
* Hornet
iii. Formicids
* Fire ants * Harvester ants
19 April 2013 9

Species of Hymenoptera and their
geographical distribution.
Freeman TM: Hypersensitivity Hymenoptera stings, N Engl J Med 351:1978–1984, 2004.)
19 April 2013 10

Cont.
Freeman TM: Hypersensitivity Hymenoptera stings, N Engl J Med 351:1978–1984, 2004.)
19 April 2013 11

Pathogenesis
Localized skin responses to
biting insects are caused
primarily by vasoactive or
irritant materials derived from
insect saliva, and rarely occur
from IgE-associated responses
19 April 2013 12

Cont.
Systemic IgE-mediated allergic
reactions to salivary proteins
of biting insects such as
mosquitoes are reported but
uncommon.
19 April 2013 13

Cont.
IgE antibody–mediated allergic
responses to airborne
particulate matter
carrying insect emanations
contribute to:
1. Seasonal
2. Perennial
symptoms affecting the upper
and lower airways
19 April 2013 14

Seasonal allergy
Attributed to exposures to a
variety of insects, particularly
aquatic insects such as the caddis
fly and midge, or lake fly, at a
time when larvae pupate and
adult flies are airborne
19 April 2013 15

Perennial allergy
Attributed to sensitization
to insects such as cockroaches
and ladybugs as well as house
dust mite
19 April 2013 16

Hymenoptera venoms
Contain numerous components
with toxic and harmacologic
activity and with allergenic
potential.
These constituents include:
1.Vasoactive substances such as
histamine, acetylcholine, and
kinins
2.Enzymes such as phospholipase
and hyaluronidase
3.Apamin4. Melittin5. formic acid
19 April 2013 17

Cont.
The majority of patients who
experience systemic reactions
after Hymenoptera stings have
IgE-mediated sensitivity to
antigenic substances in the
venom.
19 April 2013 18

i. Honey bees are only capable of
stinging a person once.
Honey Bee
iii. As the honey bee flies away, it
become eviscerated and dies.
ii. The honey bee is the only
stinging insect that leaves its
stinger and venom sac in the
skin of its victim, due to the
barbed configuration of the
stinger.
19 April 2013 19

Yellow Jacket
i. Wasp-like insects that live in
mounds built into the ground
iii. They are commonly found
around garbage cans and
picnic areas where food and
sugary drinks are abundant
ii. They tend to be very aggressive
insects, and will often sting
without provocation.
19 April 2013 20

Hornet
Hornets, including yellow and white-
faced hornets, build paper- mache type
nests in trees and shrubs
Some hornets look very much like
yellow jackets and can be difficult to
distinguish
These insects may be very aggressive,
and a sting may be provoked by a minor
disruption in their environment.
19 April 2013 21

Wasps
Wasps build honey-comb nests
under the eaves of a house, or in a
tree, shrub or under patio
furniture.
They tend to be less aggressive
than yellow jackets and
hornets, and mostly feed on
insects and flower nectar.
http://science.howstuffworks.com
19 April 2013 22

Bumblebees
Bumblebees rarely sting people
because they are non-aggressive
and typically mild mannered
They generally will sting only if
provoked
They nest in the ground or in piles of
grass clippings or wood
19 April 2013 23

Fire Ant
Fire Ant bites are generally quite painful
The bite of a fire ant characteristically
Will form into a white pustule within
a day or two
Scratching these pustules can lead to
local infection and scars
It is not unusual to sustain multiple
bites, generally on the feet and hands
19 April 2013 24

Clinical Manifestations
Insect bites are usually urticarial
but may be papular or vesicular
Papular urticaria affecting the lower
extremities in children is usually caused
by multiple bites
IgE antibody–associated immediate- and
late-phase allergic responses to mosquito
bites sometimes mimic cellulitis
19 April 2013 25

Clinical reactions to stinging
venomous insects
Are categorized as:
6.Delayed/Late
1. Local
2. Large local
3. Generalized cutaneous
4. Systemic
5. toxic
19 April 2013 26

Cont.
1.Simple local reactions
i. Involve limited swelling
ii. Pain
iii. Generally last <24 hr.
2.Large local reactions
i. Develop over hours and days
ii. involve swelling of extensive
areas (>10 cm) that are
contiguous with the sting site
iii. May last for days
19 April 2013 27

Cont.
3.Generalized cutaneous reactions
Typically progress within minutes and
include cutaneous symptoms of :
i. Urticaria ii. Angioedema
iii. Pruritus
beyond the site of the sting
4.Systemic reactions
are identical to anaphylaxis from other
triggers and may include symptoms of :
i. Generalized urticaria
ii .Laryngeal edema
iii. Bronchospasm
iv. Hypotension
19 April 2013 28

Cont.
5. Toxic reactions
Stings from a large number of insects at
once may result in toxic reactions of :
i. Fever ii. Malaise iii. Emesis iv. Nausea
owing to the chemical properties of the
venom in large doses.
6.Delayed/Late reactions
i. Serum sickness
ii. Nephrotic syndrome
iii. Vasculitis
iv. Neuritis
v. Encephalopathy
may occur as delayed/late reactions to
stinging insects
19 April 2013 29

Inhalant allergy
Caused by insects results in clinical
disease similar to that induced by
other inhalant allergens such as
pollens
Depending on individual sensitivity
and exposure, reactions may result in
seasonal or perennial
rhinitis, conjunctivitis, and asthma
19 April 2013 30

Diagnosis
Generally evident from:
i. History of exposure
ii. Typical symptoms
iii. Physical findings
The diagnosis of Hymenoptera allergy
rests in part on the identification of
venom-specific IgE by prick skin testing
19 April 2013 31

Cont.
The primary reasons to pursue testing
are to confirm reactivity when:
i. Venom immunotherapy (VIT) is
being considered
ii. It is clinically necessary to confirm
venom hypersensitivity as a cause of
a reaction
19 April 2013 32

Cont
. Venoms of five Hymenoptera (
1.Honeybee
2.Yellow jacket
3. Yellow hornet
4. White-faced hornet
5. Wasp)
as well as the jack jumper ant
and whole-body extract of fire ant
are available for skin testing
Skin tests are usually accurate within
1 wk of a sting reaction, but
occasionally a refractory period is
observed that warrants retesting after 4-
6 wk if the initial results are negative
19 April 2013 33

The diagnosis of inhalant
insect allergy
May be evident from a history of
typical symptoms induced
seasonally in specific geographic
regions
Skin prick or in vitro
immunoassay tests for specific
IgE to the insect are used to
confirm inhalant insect allergy
19 April 2013 34

Treatment
i. Cold compresses
ii. Topical medications to relieve itching
iii. occasionally the use of
a. systemic antihistamine
b. oral analgesic
are appropriate
Stingers should be removed promptly by
scraping, with caution not to squeeze the
venom sac because doing so could inject
more venom
For local cutaneous reactions
19 April 2013 35

Cont.
Sting sites rarely become
infected, possibly owing to the
antibacterial actions of venom
constituents
Vesicles left by fire ant stings that
are scratched open should be
cleansed to prevent secondary
infection
19 April 2013 36

Cont.
Therapies may include:
i. Oxygen
ii. Epinephrine
iii. Intravenous saline
iv. Steroids
v. Antihistamines
Anaphylactic reactions
19 April 2013 37

Venom
Immunotherapy(VIT)
Hymenoptera VIT is highly
effective (95-97%) in decreasing
the risk for severe anaphylaxis.
The selection of patients for VIT
depends on several factors
19 April 2013 38

Indications for venom immunotherapy
against winged Hymenoptera
SYMPTOMS AGE
SKIN TEST/IN VITRO
TEST
RISK OF
SYSTEMIC
REACTION IF
UNTREATED
(%)*
VIT
RECOMMENDE
D
Large local
reaction
Any Usually not indicated 4-10
Usually not
indicated
Generalized
cutaneous
reaction
≤16 yr Usually not indicated 9-10
Usually not
indicated
≥17 yr
Positive result 20 Yes
Negative result — No
Systemic
reaction Any
Positive result
Child: 40
Adult: 60-70
Yes
Negative result
— Usually no
*Risks generally decrease after 10 yr
19 April 2013 39

Prevention
Avoidance of stings and bites is essential
To reduce the risk of stings,
sensitized individuals should:
i. Avoid attractants such as
perfumes and bright-colored
clothing outdoors
ii. Wear gloves when gardening
iii. Wear long pants and shoes
with socks when walking in
the grass or through fields
19 April 2013 40

Cont.
Typical insect repellents do not
guard against Hymenoptera.
Nests of these insects should be
removed if they are close to the
home
19 April 2013 41

Cont.
Individuals who have had
generalized cutaneous or
systemic reactions to
Hymenoptera stings should
have immediate access to self-
injectable epinephrine
The individual at risk for
anaphylaxis from an insect
sting should also wear an
identification bracelet
indicating the allergy
19 April 2013 42

Cont.
Avoidance of the insect is the
preferred management of
inhalant allergy
Immunotherapy is occasionally
undertaken in such cases, but
beneficial results have not been
thoroughly documented.
19 April 2013 43

References
19 April 2013 44
1. http://www.acaai.org/allergist/allergies/types/inse
ct-sting-allergies
2. http://www.theonlineallergist.com
3. Freeman TM: Hypersensitivity
Hymenoptera stings, N Engl J Med 351:1978–
1984, 2004.)
4. http://www.webmd.com/allergies/guide/insect-
stings
5. http://www.aaaai.org/conditions-and-
treatments/library/allergy-library/stinging-insect-
allergy
6. http://science.howstuffworks.com
7. Scott H. Sicherer,Donald Y.M. Leung. Insect
Allergy.(In) Robert M. Kliegman, MD, and
Richard E. Behrman, MD. Nelson Textbook of
Pediatrics - Chapter 140

Insect allergy

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