Immunotherapy
Immunotherapy (also known as desensitization) consists of giving
gradually increasing quantities of an allergen to a person who has
been proven to be allergic and to develop symptoms due to that
particular allergen.
The aim of immunotherapy is to change the sensitivity of the immune
system, so that it no longer reacts to the allergen, and so
prevents an allergic reaction when the person comes in contact with
the allergen. People treated with immunotherapy show either a
complete tolerance to the allergen (which means that they develop
no symptoms when coming in contact with it) or an important
reduction in their symptoms and their need for medication.
Immunotherapy does not work in all allergic diseases. It is a very
effective treatment in people with allergy to bee or wasp venoms.
It has also been proven to be effective in allergic rhinitis (in
people with sensitisation to pollens, house dust mites and animal
dander) and in some cases of mild asthma. The role of immunotherapy
in other allergic diseases is currently under investigation.
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Immunotherapy is usually administered in subcutaneous (under the
skin) injections. These must be given weekly at the beginning of
the treatment and then, as the dose of injected allergen is
increased, at increasing intervals. When reaching the maximal dose
that can be injected safely in one injection, the injections are
usually administered at 4-6 week intervals.
Improvement of symptoms can be noticed from the first few weeks or
months of treatment (the interval varies with the person and
condition) but the treatment needs to be continued for 3-5 years to
be fully effective. In most patients the beneficial effects of
immunotherapy last for years or even life-long after the cessation
of treatment, if this was administered for the recommended
period.
In the last few years administration of the allergen solution
through sublingual (under the tongue) route has become
possible.
This is an easier way of administration as it can be taken by
patients at home, without needing medical supervision and thus
saving them from the regular trips to the doctor and also from the
pain of injections. Similar to the injectable route, sublingual
administration of the allergen solution needs to be continued for
3-5 years to be effective.
Immunotherapy, even though very efficient in some cases, cannot be
given to all people due possible severe side effects.
The main risk is the development of a generalized allergic reaction
(anaphylaxis) which may put the patient’s life in danger. Also,
people with moderate to severe asthma run the risk of developing
severe bronchospasm which can result in death. Furthermore,
immunotherapy must be given with caution to people suffering from
heart problems (who have a higher risk of severe heart symptoms if
they develop an anaphylactic attack).
For all these reasons, the decision to start immunotherapy must
only be made by an allergy specialist, who has to take into
consideration and balance possible benefits as well as possible
risks for each individual patient.
