Hyposensitization (obsolete: desensitization), also called specific immunotherapy (SIT) or allergy vaccination, is a procedure used in allergology. This form of therapy is used to treat or cure allergies and is considered their only causal treatment. An allergy is a congenital or acquired change in the immune system‘s response pattern to foreign, harmless substances. These substances are also called allergens. Upon contact with the allergen, the body reacts with an exuberant immune response to the skin, vascular system, conjunctives (conjunctiva), nasal mucosa, pharyngeal mucosa, bronchial mucosa, or gastrointestinal tract. Hyposensitization desensitizes the patient to the allergen causing the allergy and creates allergy tolerance. Hyposensitization is indicated when the following conditions are met:
- Evidence of a type 1 allergy. Hyposensitization is ineffective in non IgE-mediated allergies.
- The allergen has been determined with certainty by testing.
- Only a few allergens may be responsible for the allergy.
- Exposure prophylaxis is not possible! Occupational allergies can be better “treated” by a change of occupation.
Hyposensitization is particularly suitable for children and young adults, because here the effectiveness is best. Therapy is indicated in cases of severe allergy that can not be controlled with allergen abstinence (elimination of pets, etc.) or pharmacotherapy (eg, antihistamines). Subcutaneous specific immunotherapy for insect venom allergy (VIT, English venom immunotherapy) is considered one of the most effective hyposensitization procedures worldwide.
Indications (areas of application)
- Insect venom allergy – wasp or bee venom.
- Pollen and grass allergy
- Dust mite allergy
- Allergic rhinoconjunctivitis – hay fever
- Bronchial asthma
- In individual cases in: Drug allergy, mold allergy, animal epithelial and food allergy.
Contraindications
- Partial or uncontrolled bronchial asthma (FEV1 <70% of set point despite adequate therapy).
- Autoimmune diseases (excl. Hashimoto’s thyroiditis, rheumatoid arthritis, ulcerative colitis and Crohn’s disease, and type 1 diabetes)
- Immunodeficiency
- Malignant neoplasms with current disease value.
- Initiation of SIT during pregnancy; continuation of SIT at the onset of pregnancy does not cause any problems
- Beta-blockers (also as eye drops): A.I. for SCIT, but not for SLIT.
- ACE inhibitors: A.I. for SCIT with insect venom.
- Cardiovascular disease with increased risk of adverse effects from adrenaline administration.
SIT = specific immunotherapy SCIT = subcutaneous immunotherapy SLIT = sublingual immunotherapy.
A claim to completeness of the above contraindications does not exist!
The procedure
The procedure is practically performed as follows: First, allergy diagnostics (e.g., prick test) are used to determine the allergen. This allergen is initially injected into the patient at a low concentration for hyposensitization. The allergen preparation is standardized and specifically selected for the patient’s allergy. It is then administered in increasing concentrations at regular intervals until the so-called maintenance dose is reached. This is the dose that just does not trigger any side effects. This maintenance dose is now injected regularly over a period of three to five years to ensure the ongoing success of the therapy. Perennial immunotherapy (PIT) is better than short-term therapy (preseasonal specific immunotherapy, PSIT) for improving the symptoms of pollen allergy. Allergen extract is applied by different routes:
- Subcutaneous injection (SCIT) – the most effective and common method, used mainly for allergies of the respiratory tract (respiratory tract) and insect venom allergy.
- Oral administration – by means of an aqueous extract or capsule, especially in birch allergy and dust mite allergy.
- Local administration nasally, bronchially, and sublingually (under the tongue; SLIT).
The average dosage of, for example, the hymenopteran venom is 100 µg in children (possibly also 50 µg) and adults. The exact mechanism of action of hyposensitization has not yet been elucidated. However, the following mechanisms of action are known: In allergic patients, the TH2-mediated immune response dominates. This proallergic response is gradually shifted to an anti-allergic TH1-mediated immune response. In addition, the number of mast cells is reduced. These cells release the mediators (histamine) for the allergic response, resulting in clinical allergy. A good body of data on the efficacy of sublingual specific immunotherapy (SLIT) exists for the following indications: Rhinoconjunctivitis due to pollen allergy in children and adults and in adults with cotton allergy, house dust mite allergy in adults, allergic bronchial asthma, and allergic asthma due to grass pollen.
After treatment
Hyposensitization is not without danger, as hypersensitivity reactions, including anaphylactic shock, can occur at any time. Because this reaction always occurs within a 30-minute period after allergen application, the patient must be monitored during this time so that emergency medical measures can be taken if complications arise.
Potential complications
Side effects of SCIT (subcutaneous immunotherapy): allergic reactions up to and including anaphylaxis Side effects of SLIT (sublingual immunotherapy): compared with SCIT, mild side effects are more common and serious side effects are less common
Other side effects include pain, itching, erythema, edema, or worsening of the underlying disease. Because of the potential for serious anaphylaxis from SCIT, the practice must be equipped to treat anaphylaxis. Minimum equipment includes: Defibrillator, IV, epinephrine, antihistamine, beta-2 sympatomimetic (for inhalation), and corticosteroids (for intravenous injection).
Benefits
Hyposensitization is the most effective and only long-term measure against allergy. Allergies can significantly reduce quality of life and, in individual cases, pose a constant acute threat to life. In addition, this therapy reduces the number of allergy-related hospitalizations and thus reduces the cost of medication. For these reasons, hyposensitization is recommended.
