What is hyposensitization?
Hyposensitization is also called allergen immunotherapy (AIT), desensitization or specific immunotherapy (SIT). More rarely, the term “allergy vaccination” is used.
The name of the therapy is also derived from this mode of action: “hypo” stands for “less”, and “sensitization” for the development of a defense reaction of the immune system against a certain substance.
Only causal treatment
In principle, there are three ways to treat an allergy:
- exposure prophylaxis: avoidance of the allergy-causing substance (allergen abstinence)
- Medicinal treatment
- Hyposensitization
What happens in the body during an allergy?
The human immune system is designed to protect the body from harmful influences, for example from bacteria and viruses. The immune system recognizes these mainly by their surface structure and forms defensive substances (antibodies) if necessary.
Why some people are allergic to certain substances and others are not has not yet been conclusively clarified.
In this context, the approach of hyposensitization can best be described as a kind of “confrontation therapy” with the allergen.
When is hyposensitization performed?
Hyposensitization is recommended by physicians in the following cases, among others:
- if there is a risk of secondary diseases such as allergic bronchial asthma, i.e. a so-called floor change of the allergy from the upper to the lower respiratory tract.
- in case of severe side effects of the drug therapy.
Due to uncertain efficacy and possible adverse reactions, hyposensitization for animal dander and food allergy has not been recommended in most cases to date. However, oral immunotherapy (OIT) is now approved in the EU and Switzerland for four- to 17-year-old children and adolescents with peanut allergy (see below).
Hyposensitization in children
What can hyposensitization do?
Hyposensitization can
- reduce the symptoms of an existing allergy.
- reduce the risk of allergic asthma.
- support the therapy of mild forms of asthma.
- probably prevent further type I allergies from developing.
- help reduce the need for allergy or asthma medications.
What do you do during hyposensitization?
Depending on how the allergen is administered, physicians distinguish between two main forms of hyposensitization:
- subcutaneous immunotherapy (SCIT): In classic hyposensitization, the allergen is injected under the skin.
- sublingual immunotherapy (SLIT): The allergen is placed under the tongue (as a tablet) or dripped.
Subcutaneous immunotherapy (SCIT)
Before each dose increase, the physician pays attention to any side effects of the previous injection and adjusts the vaccination schedule if necessary. If necessary, he or she can also prescribe medication to counter any allergic symptoms that may occur. For example, antihistamines are used. These inhibit the effect of the body’s own messenger substance histamine, which plays a key role in allergic reactions of the immediate type.
Sublingual immunotherapy (SLIT)
Duration of hyposensitization
The duration of allergen administration depends on the underlying allergy. The average duration of treatment is three years, and three to five years for wasp venom allergy. In the case of bee venom allergy, hyposensitization is carried out indefinitely – the physician must administer a “maintenance vaccination” regularly in the long term.
In addition, the physician may perform a skin test with the antigen in question and draw blood from the patient to determine the immune response: In type I allergic patients, specific immunoglobins E (IgE) are usually found in the blood. This class of antibodies plays an important role in triggering immediate-type allergic reactions. When the IgE level in the blood has decreased or completely normalized, hyposensitization is considered successfully completed.
Overall, hyposensitization is a very safe procedure. Side effects may include allergic reactions to the administered allergen such as sneezing, eye watering, swelling or itching.
More severe but easily treatable side effects that are possible with hyposensitization include wheals all over the body (urticaria = hives) and swelling in the neck area (Quincke’s edema, angioedema).
In order to observe how the patient reacts, he usually has to stay in the practice for half an hour for observation after each therapy session. In addition, he should avoid physical stress and alcohol on the day in question.
When should allergy sufferers not start hyposensitization?
Not every patient suffering from one of these allergies should undergo hyposensitization. The most common exclusion criteria for hyposensitization are:
- current cancer
- cardiovascular disease or taking beta-blockers
- severe autoimmune diseases or immunodeficiencies
- uncontrolled asthma
- untreated chronic infection (such as HIV or hepatitis C)
- severe psychiatric illnesses
- poor adherence to therapy (adherence)
- inflammatory bowel diseases and open wounds in the oral cavity (during SLIT)
Even if one of the contraindications mentioned above is present, hyposensitization is possible in individual cases. Patients are best advised to discuss the benefits and risks of such treatment with their physician.
