Allergen immunotherapy (also termed
desensitization) is a medical treatment aiming at
patients suffering from allergies that are insufficiently
controlled by symptomatic treatments.
Sub-lingual immunotherapy is used by physicians in many countries: it involves
putting drops or a tablet of allergen extracts under the tongue to swallow the
It allows the body to become tolerant of the allergen by absorbing the allergen
through the stomach lining. The treatment is usually taken at home. Sublingual
immunotherapy is currently commercialized and used in most European and
South American countries, and in Australia and Asian countries. In most
European countries, national regulations allow marketing of allergen products
as "named patient preparations" (NPPs). In the United States, it has not yet
received FDA approval, though off-label prescription is becoming common.
Subcutaneous immunotherapy is the historical route of
administration and consists of allergen extract injections
which can only be performed with a medical observation.
Subcutaneous immunotherapy protocols generally involve
weekly injections during a build-up phase, followed by
monthly maintenance injections for a period of 3–5 years.
The British physicians Noon and Freeman were the first
researchers to test pollen allergen immunotherapy in a patient
cohort. Noon and Freeman, researchers at the Department of
Therapeutic Inoculation at St. Mary’s Hospital in London,
published their findings in The Lancet in 1915.Building on the
observations of his predecessors Bostock, Blackley and Dunbar,
Noon noted that hay fever patients “sometimes become cured”
and that this was possibly because they “have had the good
fortune to develop an active immunity against the toxin.” He
hypothesized that by injecting hay fever patients with small
amounts of a pollen “toxin”, a state of immunity could be
Mechanism of therapeutic action
In desensitization immunotherapy the aim is to restore
tolerance to the allergen by reducing its tendency to
induce IgE production. Patients are desensitized by
injection with escalating doses of allergen, starting with
tiny amounts, an injection schedule that gradually
decreases the IgE-dominated response. The mechanisms
underlying desensitization therapy are complex, but the
key to success seems to be the induction of regulatory T
cells secreting IL-10 and/or TGF-beta, which skew the
response away from IgE production.
Sublingual immunotherapy involves, putting drops or a tablet of allergen extract under the tongue and
then swallowing the extract. Besides its efficacy, sublingual immunotherapy is known to have a better
safety profile than subcutaneous immunotherapy and one of the significant benefits of sublingual
immunotherapy .is also that the patient can take the treatment at home
Today allergen immunotherapy is available in tablet form (for grass pollens).
No other method of administration of allergen immunotherapy has reached this level of proof
and provides such a favorable benefit/risk ratio. Allergen immunotherapy has therefore acquired a
level of evidence equivalent to that of “conventional” drugs, both in terms of documentation of its
pharmaceutical quality and the rigor of its production, and its terms of demonstration of its clinical
efficacy and safety for patients.
Prescribed by an allergy specialist, injections of allergens are
administered in a medically controlled environment and followed
by an observation period of 30 minutes. These pain-free injections
are given in order to subcutaneously (under the skin) administer
the allergen on the arm between the elbow and shoulder.
Allergen injections are started at very low doses. The dose is
gradually increased on a regular (and usually weekly) basis, until a
"maintenance" dose is reached. Once the maintenance dose is
reached, the injections are administered less often (every two to
four weeks), still on a regular basis. After 3 years or 3 seasons (if
seasonal allergy) of successful completion of immunotherapy, long-
term protection can be expected.