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| Allergen Immunotherapy
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Allergen immunotherapy is the practice of administering gradually increa-
sing quantities of an allergen extract to an allergic subject to ameliorate
the symptoms associ
ated with the subsequent exposure to the causative allergen.
History
Immunotherapy was introduced to treat allergic rhinitis by Noon and Fre-
eman in
1911. Since then, immunotherapy has been used to treat allergic diseases caused by
inhalant allergens and is an effective treatment for patients with seasonal or peren
nial allergic rhinoconjunctivitis and asthma.
Indications
Immunotherapy could treat allergic rhinitis, allergic asthma, allergic conjunctivitis,
and insect sting hypersensitivity. Treatment of food allergy, urticaria with immunotherapy is not considered appropriate. Immunothe-
rapy may also prevent the development of asthma in patients with allergic rhinitis, and may prevent onset of new sensitization in allergic patients.
Routes
Conventional administering form of immunotherapy is subcutaneous injection. Subcutaneous
immunotherapy (SCIT) normally involves a weekly subcutaneous injection of an
extract of the allergen in solution, in increasing doses until a standard maintenance
dose is reached. The dose is then injected subcutaneously on a regular basis for not
less than 3 years. However in 1986 the British Committee on Safety of Medicines
spuriously reported several deaths caused by SCIT, which were subsequently shown
to be the result of human error. In response to this, alternative routes (e.g. sublin
gual, oral, nasal) of administration were investigated.
Of those, sublingual immunotherapy (SLIT), in which liquid drops or allergen tablets
are placed under the tongue for 1-2 minutes before being swallowed, was found to
be viable. SLIT has been reported similar efficacy compared with SCIT. The significant advan
tage of SLIT is its safety. There is no any severe adverse event being reported by
now. It is now widely used throughout Europe, Asia, South America, and other
regions. It has received approval from the World Health Organization (WHO) working
group and the international Allergic Rhinitis and its Impact on Asthma (GINA) consensus group.
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