Blood-borne allergens refers to all substances
introduced into the body through a break in the skin barrier.
They are then transported in the body via the blood
circulation.
Consequently, their contact with immune cells is accelerated
compared to a normal allergic reaction, which accounts for their
speed in triggering symptoms of allergy in such cases. However,
such allergens only rarely trigger a systemic reaction.
As is observed with food allergens, medicinal products administered
by parenteral route can enter the category of humeral allergens.
Since medicinal products represent a separate category of
allergens, they will be discussed under the heading medicinal
products.
Humeral allergens thus are mainly hymenoptera venom or that of mosquitoes and horseflies.
Hymenoptera:
These are the main insects implicated in allergy to insect
stings.
We can differentiate bees, wasps, and more rarely hornets.
Hymenoptera stings account for one of the main causes of
anaphylactic shock in France.
Bees and bumblebees
(apids):
Their abdominal striations are brown and yellow. In their natural
habitat they are calm andsting only when feel threatened or when
their nest is in danger. When a bee stings, it dies because part of
its digestive tract is expelled with the stinger. A bumblebee is
less aggressive.
Wasps and hornets
(vespids):
Their abdominal striations are black and yellow, they are larger
than bees and are naturally agressive, especially in autumn when
food is rare. In wasps, the stinger is not systematically lost, and
thus it can sting several times.
Insect stings generate 2 types of reactions:
- A local allergic reaction at the sting site which can be differentiated from the normal reaction by the extent of the papule (greater than 10 cm versus about 2 cm for a normal reaction).
This reaction is painful and prurigeneous and can extend to joints adjacent to the site of the sting. This reaction is also of early onset (within 30 minutes of a sting), lasts about 24 hours and its course and outcome tend to be non-serious, except for a sting within a subject's mouth, which can generate edema with a risk of asphyxia. - A systemic allergic reaction: such a reaction affects about 0.38-3.9% of the population
and 16-43% of beekeepers. It is characterized by various symptoms depending on its degree of
severity (4 stages according to Mueller's classification): - Stage I or a mild systemic reaction: subject presents generalized urticaria with angio-edema, pruritus accompanied by anxiety and a sensation of malaise.
- Stage II or strong systemic reaction: the subject presents one or more symptoms of stage I, together with at least two of the following symptoms:
- Pressure on the chest
- Abdominal pain
- Nausea
- Diarrhea
- Dizziness - Stage III or a serious systemic reaction: the subject presents one or more symptoms of stage II, together with at least two of the following symptoms:
- Dyspnea
- Dysphagia
- Dysphony
- Confusion
- Feeling of impending death - Stage IV or anaphylactic shock: the subject presents one or more symptoms of stage III, in combination with at least two of the following symptoms:
- Cyanosis
- Hypotension
- Circulatory collapse
- Loss of consciousness
- Syncope
- Incontinence
Stages III and IV are the most serious: they are life threatening in the short term and require early treatment using epinephrine.
Stings from mosquitoes and horesflies:
Allergic reactions caused by such stings are of the local type, no
systemic reactions are
observed. They can be of immediate or delayed-onset reaction. H1
receptor antihistamines have a
protective effect on such reactions because they tend to diminish
skin reactions