Topical application of antihistamines to the skin is not
recommended.
An oral antihistamine may be used to prevent urticaria,
and for the treatment of acute urticarial rashes, pruritus,
insect bites, and stings. Antihistamines are also used in the
management of nausea and vomiting, of migraine, and the
adjunctive management of anaphylaxis and angioedema.
Thenon-sedatingantihistamine cetirizine hydrochloride
p. 174 is safe and effective in children. Other non-sedating
antihistamines that are used include acrivastine p. 173 ,
bilastine p. 173 , desloratadine p. 174 (an active metabolite of
loratadine p. 176 ), fexofenadine hydrochloride p. 175 (an
active metabolite of terfenadine), levocetirizine
hydrochloride p. 175 (an isomer of cetirizine hydrochloride),
loratadine, and mizolastine p. 176. Most non-sedating
antihistamines are long-acting (usually 12 – 24 hours). There
is little evidence that desloratadine or levocetirizine
hydrochloride confer any additional benefit—they should be
reserved for children who cannot tolerate other therapies.
Sedatingantihistamines are occasionally useful when
insomnia is associated with urticaria and pruritus. Most of
the sedating antihistamines are relatively short-acting, but
promethazine may be effective for up to 12 hours.
Alimemazine tartrate p. 177 andpromethazinehave a more
sedative effect than chlorphenamine maleate p. 178 and
cyclizine p. 260. Chlorphenamine maleate is used as an
adjunct to adrenaline/epinephrine p. 136 in the emergency
treatment of anaphylaxis and angioedema.Allergen immunotherapy
Immunotherapy using allergen vaccines containing house
dust mite, animal dander (cat or dog), or extracts of grass
and tree pollen can improve symptoms of asthma and
allergic rhinoconjunctivitis in children. A vaccine containing
extracts of wasp and bee venom is used to reduce the risk of
severe anaphylaxis and systemic reactions in children with
hypersensitivity to wasp and bee stings. An oral preparation
of grass pollen extract (Grazax®) is also licensed for disease-
modifying treatment of grass pollen-induced rhinitis and
conjunctivitis. Children requiring immunotherapy must be
referred to a hospital specialist for accurate diagnosis,
assessment, and treatment.
Omalizumab p. 164 is a monoclonal antibody that binds to
immunoglobulin E (IgE). It is licensed for use as additional
therapy in children over 6 years with proven IgE-mediated
sensitivity to inhaled allergens, whose severe persistent
allergic asthma cannot be controlled adequately with high-
dose inhaled corticosteroid together with a long-acting beta 2
agonist. Omalizumab should be initiated by physicians
experienced in the treatment of severe persistent asthma.
Omalizumab is also indicated as add-on therapy for the
treatment of chronic spontaneous urticaria in patients who
have had an inadequate response to H 1 antihistamine
treatment.Anaphylaxis and allergic emergencies
Anaphylaxis
Anaphylaxis is a severe, life-threatening, generalised or
systemic hypersensitivity reaction. It is characterised by the
rapid onset of respiratory and/or circulatory problems and is
usually associated with skin and mucosal changes; prompt
treatment is required. Children with pre-existing asthma,
especially poorly controlled asthma, are at particular risk of
life-threatening reactions. Insect stings are a recognised risk
(in particular wasp and bee stings). Latex and certain foods,
including eggs,fish, cow’s milk protein, peanuts, sesame,
shellfish, soy, and tree nuts may also precipitate anaphylaxis
(see Food allergy p. 60 ). Medicinal products particularly
associated with anaphylaxis include blood products,
vaccines, allergen immunotherapy preparations,
antibacterials, aspirin p. 91 and other NSAIDs, and
neuromuscular blocking drugs. In the case of drugs,anaphylaxis is more likely after parenteral administration;
resuscitation facilities must always be available for injections
associated with special risk. Refined arachis (peanut) oil,
which may be present in some medicinal products, is
unlikely to cause an allergic reaction—nevertheless it is wise
to check the full formula of preparations which may contain
allergens.
Treatment of anaphylaxis
Adrenaline/epinephrine provides physiological reversal of
the immediate symptoms associated with hypersensitivity
reactions such asanaphylaxisandangioedema.
First-line treatment includes:
.securing the airway, restoration of blood pressure (laying
the childflat and raising the legs, or in the recovery
position if unconscious or nauseous and at risk of
vomiting);
.administering adrenaline/epinephrine byintramuscular
injection; the dose should be repeated if necessary at
5 -minute intervals according to blood pressure, pulse, and
respiratory function;
.administering high-flowoxygenandintravenousfluids;
.administering an antihistamine, such as chlorphenamine
maleate, by slow intravenous injection or intramuscular
injection as adjunctive treatment given after adrenaline.
.Administering an intravenous corticosteroid such as
hydrocortisone p. 440 (preferably as sodium succinate) is
of secondary value in the initial management of
anaphylaxis because the onset of action is delayed for
several hours, but should be given to prevent further
deterioration in severely affected children.
Continuing respiratory deteriorationrequires further
treatment withbronchodilatorsincluding inhaled or
intravenous salbutamol p. 156 , inhaled ipratropium bromide
p. 153 , intravenous aminophylline p. 167 , or intravenous
magnesium sulfate p. 597 [unlicensed indication] (as for
acute severe asthma); in addition to oxygen, assisted
respiration and possibly emergency tracheotomy may be
necessary.
When a child is so ill that there is doubt about the
adequacy of the circulation, the initial injection of
adrenaline/epinephrine may need to be given as adilute
solution by the intravenous route,orbytheintraosseous route
if venous access is difficult; for details see
adrenaline/epinephrine.
On discharge, child should be considered for further
treatment with an oral antihistamine and an oral
corticosteroid for up to 3 days to reduce the risk of further
reaction. The child, or carer, should be instructed to return
to hospital if symptoms recur and to contact their general
practitioner for follow-up.
Children who are suspected of having had an anaphylactic
reaction should be referred to a specialist for specific allergy
diagnosis. Avoidance of the allergen is the principal
treatment; if appropriate, an adrenaline/epinephrine auto-
injector should be given for self-administration or a
replacement supplied.
Intramuscular adrenaline (epinephrine)
Theintramuscular route is thefirst choice routefor the
administration of adrenaline/epinephrine p. 193 in the
management of anaphylaxis. Adrenaline/epinephrine is best
given as an intramuscular injection into the anterolateral
aspect of the middle third of the thigh; it has a rapid onset of
action after intramuscular administration and in the shocked
patient its absorption from the intramuscular site is faster
and more reliable than from the subcutaneous site.
Children with severe allergy, and their carers, should
ideally be instructed in the self-administration of
adrenaline/epinephrine by intramuscular injection.
Prompt injectionof adrenaline/epinephrine is of paramount
importance. The adrenaline/epinephrine doses
recommended for the emergency treatment of anaphylaxis
by appropriately trained healthcare professionals are based172 Allergic conditions BNFC 2018 – 2019
Respiratory system3