Allergen-specific immunotherapy involves administering increasing doses of allergens to induce tolerance. It works by inducing regulatory T cells that reduce the allergic response. Immunotherapy is effective for allergic rhinitis, asthma, and insect sensitivity. The goals are to eliminate symptoms or reduce medication needs. It is a safe and effective therapy when administered properly to suitable candidates.

1. Dr. Himanshu S Dave
Department of Pediatrics
NRCH, New Delhi

2.  Allergen specific immunotherapy (SIT) :
• Defined as a gradual immunizing process in
which increasing doses of antigens responsible
for causing allergic symptoms are administered
to a patient to induce increased tolerance to the
allergen when natural exposure occurs.
• Known as hypo sensitization or desensitization

3.  The benefit of specific immunotherapy is
dependent on both the dose and the route of
administration.
 Mechanism : Not fully understood . The
current consensus is that specific immunotherapy
works by inducing allergen-specific T regulatory
cells that reduce the late-phase response to the
allergen.
 It was introduced by Noon in 1911 by
inoculating pollen extracts in cases of hay fever

4.  During a period of years, specific immuno
therapy typically induces an allergen-specific
IgG response.
 In the past, this type of antibody was called
blocking antibody, although there is no
evidence that it actually blocks the allergic
response or has any physiologic role.

5.  Immunotherapy is effective in :
• Allergic rhinitis
• Allergic asthma
• Insect stinging insect sensitivity
• Whereas it is not effective in eczema., Food allergy,
latex allergy and urticaria.

6.  Goals of immunotherapy : Complete
disappearance of symptoms with use of
medications less or in low doses with no
significant side effects or symptoms should be
at a tolerable level even after completion of
immunotherapy.

8.  Insufficient response to pharmacotherapy.
 Insufficient response to environmental control.
 Significant side-effects to medical therapy.
 Patients who have perennial disease.
 Poor compliance to medical regimen.
 Possible prevention of asthma from allergic
rhinitis.

10.  Severe asthma – FEV1 < 70% with active Rx.
 Contraindications for epinephrine (Beta-
blocker).
 Immunodeficiency/auto immune diseases.
 Pregnancy.
 Malignancy.
 Psychological.
 Mentally impaired patients.
 Short expected life span < 5 years.
 Non-compliant patient.

12.  When properly administered to an appropriate
candidate, it is a safe, effective form of therapy
capable not only of reducing or preventing
symptoms, but of potentially altering the
natural history of the disease by minimizing
disease duration and preventing disease
progression.
 The use of standardized extracts is advised to
get optimal results

13.  Success of immunotherapy depends on:
• Optimal means of allergy testing
• Quality of allergen extract
• Correct initial dose of immunotherapy
• Follow-up with maintenance dose.

14.  Failure of immunotherapy is mainly due to:
• Inadequate environmental control.
• Missed diagnosis (non-allergic rhinitis)
• Failure to include allergen in SIT
• Exposure to unknown allergen
• Inadequate dose of allergen injection
• Noncompliance of schedule
• Development of new allergic sensitivities,
unrealistic patient expectations for cure and some
patients may not responded favorably to SIT itself

16.  Systemic reactions to immunotherapy:
• Occur within one hour
• Usually scattered hives
• Rarely severe anaphylaxis,
• Whereas local reactions : Occur up to 24 hours.
Incidences of fatal anaphylaxis is 1 per 2 million
injections.

17.  Common local reactions are wheals,
indurations or both mainly due to poor
injection technique.
 Patient should be under observation for 30
minutes to monitor allergic reactions.
 Patient education is essential especially for
delayed reactions

18.  At the first sign of a systemic reaction, a
tourniquet may be applied above the injection
site and epinephrine administered at a weight
appropriate dose preferably by the
intramuscular route.

20.  Schedules of allergen administration are
selected based on the sensitivity of the patient
to the allergens in the extract.
 Dose ranges from 4-12 ug administered
subcutaneously.
 Despite the established efficacy of
subcutaneous injections of causal allergens, the
therapy did not gain popularity due to risk of
systemic reactions.

21.  Primary Immunotherapy:
 To start with low doses are administered
 Can be stepped up gradually in dosage and
frequency until maintenance dose is reached.
 It has to be given for 3-5 months.

22.  Maintenance Immunotherapy:
 After attaining adequate control with twice dose, it
can be changed over to once a month dose.
 To get adequate response one year of treatment is
compulsory .
 If there is no response it can be discontinued.
 Progressive improvement occurs by 2-3 years.
 Maintenance immunotherapy is given for a period
of 3-5 years. Prediction of response is difficult.
 Extracts are stored at 2-8°C in the refrigerator for
optimal efficacy.

24.  Nasal Immunotherapy is administered as spray
allergen solution into the nose in a phased
manner but lack of significant immunologic
response led to discontinuation of this route.
 Sublingual immunotherapy is administered as
drops of high dose allergen solution
underneath the tongue which is then
swallowed. It may be started at the full
maintenance dose, without the gradual
increase in dose

25.  The common side effect of sublingual
immunotherapy is local irritation in the mouth
and under the tongue (47 to 52%).
 But it is usually transient and does not progress
to anaphylaxis.
 It has the added advantage of ease of
administration, home based therapy and
avoidance of painful injections. So it can be
advocated for children.

26.  Intrabronchial administration : Out of general
usage due to untoward side effects.
 Future strategies
• Alum depot preparations which act as
adjuvants
• Allergoids which are chemically modified
allergens
• Peptide immunotherapy which uses allergen
derived T-cell peptide epitope, recombinant
allergens and anti-IgE antibodies

28.  The process of inducing adequate
immunological response in an accelerated pace,
where in all the doses could be given within a
period of few days is termed as Rush
Immunotherapy.
 Here the doses are spaced out in 2-6 hourly
intervals so that maintenance dose is reached
within few days.

29.  The risk of Systemic Allergic reactions is high.
 It has to be undertaken where facilities for
intensive care and monitoring are available.
 Patients should be pretreated with
antihistamines and corticosteroids.

30. THANK YOU