Immunotherapy, Sublingual SLIT and Subcutaneous Injections SCIT (allergy shots)
WHAT IS SIT? Specific allergen immunotherapy (SIT) is a disease-modifying therapy is in which increasing doses of whole allergen extract are administered in increasing dose in order to desensitise the allergic subject (1).
Allergen specific immunotherapy has been shown to be effective in rigorous double-blind placebo-controlled clinical trials in both children and adults. A recent WHO position paper stated that immunotherapy is an effective treatment for patients with allergic rhinitis/conjunctivitis, allergic asthma and allergic reactions from stinging insects (2)
One year specific immunotherapy with standardized house dust mite (HDM) vaccine significantly improved symptoms and reduced medication use in mild to moderate allergic asthmatic patients. SIT also reduced skin prick test reactivity to Der p. Complying with the EAACI immunotherapy guidelines, SIT with standardized HDM vaccine was a safe treatment(3) SIT has long-term effects on asthmatic symptoms in young adults (4)
Whilst efficacious, this form of therapy is associated with the risk of adverse, IgE-mediated events including systemic anaphylaxis (1)
WHEN IS IT USED? Specific immunotherapy is only used when IgE sensitisation and presence of symptoms due to a specific allergen are confirmed.
Allergic rhinitis (hay fever), mild allergic asthma, occasionally it is used in eczema with proven sensitisation (there are contraindications).
SIT is currently offered for airborne allergy (weeds, grasses, trees, animals, house dust mites), severe systemic reaction to venom of stinging insects (bees, wasps), sensitivity to some drugs (for example in case of TB treatment, aspirin sensitivity).
NOT FOR FOOD ALLRGY SIT is not used as a method of treatment for food allergy due to severe side effects of OIT (oral immunotherapy) (there are studies where this possibility is explored, but OIT is not available as treament). At the moment the treatment for proven food allergy is strict avoidance and emergency medication in case of accidental exposure.
Some patients with mild oral symptoms with fruits (Oral Allergy Syndrome) caused due to cross-reactivity with the main allergen, may get improvement their oral symptoms when they have immunotherapy for their main condition (Allergic Rhinitis) (usually birch pollen).
HOW IS IT DONE? Specific immunotherapy can be administered in several ways: most common widely acceptable are Subcutaneous SCIT (allergy shots) the oldest (more than 100 years of experience) and Sublingual SLIT (relatively new but the safest method). There are also experimental administration routes that are not used in clinical practice (intranasal and intadermal).
SCIT In case of subcutaneous treatment usually there are weekly injections during first 3-4 months followed by monthly injections for the duration of treatment. In case of cold or other illness injections are usually postponed for up to 2 weeks or if longer the dose needs to be adjusted by the doctor. (for some vaccines schedules are different, and some patients require individual schedules)
SLIT Is used daily either in the morning or in the evening in the exact time for the duration of treatment (either tablet of sub-lingual drops). For some allergens and in cases of high sensitivity there is a need to increase dose gradually over several weeks. As the treatment is very safe patients take drops at home and come for regular check-ups every 6 months.
The medication (allergen vaccines) from different manufactures are not interchangeable, Although the main component of any vaccine is allergen its dose and preservative components are different for each manufacturer. Vaccines (and treatment approach) in the US are absolutely different comparing to vaccines used in European Countries.
DURATION As the treatment is long term and the minimum duration is three years it needs to be thought through carefully before the start as it is difficult in some countries to find highly qualified specialist to continue your treatment. Our centre participates in Global Allergy Network can help people who are already on treatment and those who just think to start.
ALLERGENS (VACCINES) Another important note: It is not possible to change vaccine during treatment from one manufacturer to another and the whole course of treatment should be with the same vaccine. It is possible to get desensitised to more than one allergen, although when allergy is not treated early and progresses to poly sensitisation the efficacy of the treatment can be lower comparing to mono-sensitisation. Current US approach is to mix allergens together (see below), in Europe different vaccines are used individually (2 different injections)
1) Mark Larche, British Medical Bulletin 2OOO;56 (No4).
2) Boquete M, Carballada F, Expósito F, González A. Allergol Immunopathol (Madr). 2000 May-Jun;28(3):89-93
3) Wang HY, Lin XP, Hao CL, Zhang CQ, Sun BQ, Zheng JP, Chen P, Sheng JY, Wu A, Zhong NS Zhonghua Jie He He Hu Xi Za Zhi. 2006 Oct;29(10):679-87
4) Cools M, Van Bever HP, Weyler JJ, Stevens WJ Allergy. 2000 Jan;55(1):69-73