Hyposensitization: information and procedure

What is hyposensitization?

Hyposensitization, also called desensitization, allergy vaccination or specific immunotherapy (SIT), is a long-term treatment method for immediate-type allergies. It is the only form of therapy available that not only alleviates the symptoms of an allergy, but also treats the causes of hypersensitivity reactions of the immune system to certain substances.

For whom is hyposensitization an option?

Desensitization is most commonly used to treat hay fever or insect venom allergies ; in the latter it can be life-saving. But hyposensitization is also possible in the case of allergic reactions to house dust mites , animal hair or mold. The following applies: The earlier the hyposensitization is started after the occurrence of an allergy, the better the chances of success. However, experts advise not to carry out the hyposensitization before the age of five.
Note: So far, no hyposensitization is possible against food or contact allergies .

In addition to alleviating the symptoms, the therapy also serves to prevent the development of allergic bronchial asthma . Because if an allergy is not treated adequately or not at all over a longer period of time, the so-called change of levels can occur, which then manifests itself in chronic asthma. This is one of the reasons why early hyposensitization is recommended.

Hyposensitization is advisable if…

• …an immediate-type allergy has been definitely diagnosed.
• …complaints occur after contact with allergens.
• …the allergy trigger is difficult to avoid, e.g. pollen.
• …treatment with medication is not effective enough.

Hyposensitization should be avoided in the following cases:

• pregnancy
• autoimmune diseases
• cancer
• severe cardiovascular disease
• severe asthma

How does hyposensitization work?

The immune system of allergy sufferers is overly sensitive to actually harmless substances in the environment. These are usually proteins contained in the relevant allergens, such as grass pollen. In order to ward off these supposed pollutants, the organism forms antibodies that cause the release of messenger substances and ultimately cause allergic reactions.

In principle, hyposensitization works in a similar way to vaccination. The patient is given the appropriate allergen in small doses that increase slightly over time. The cells of the immune system are thus given the chance to slowly get used to the allergy-triggering substance: a kind of resistance develops. As a result, fewer and fewer messenger substances are gradually released, since the allergens are no longer perceived as a threat. In addition, special cells are formed that can neutralize the allergens. The body thus learns to react appropriately, which means that allergic reactions no longer occur or only occur very weakly.
Note:The sensitization to a specific allergen is not eliminated by the hyposensitization, but only significantly reduced. This is also the reason why the term desensitization, which was used in the past, was replaced by hyposensitization.

How does the hyposensitization work?

Each hyposensitization begins with a detailed anamnesis interview . In this conversation, the doctor treating you will ask about your previous medical history and your personal circumstances and get an idea of ​​the exact symptoms and allergic symptoms. An allergy test also identifies the exact allergy trigger.

Various forms of hyposensitization can then be used. In the classic method , the relevant allergen is administered at regular intervals over a period of about three years. This form of therapy is divided into two phases, the increase phase and the maintenance phase.

• Escalation phase: During the initial phase of hyposensitization, the patient is injected subcutaneously, i.e. into the fatty tissue of the upper arm, every week with a small dose of the allergen extract. Each week the dose is increased slightly until the target maximum dose is reached. If no major problems or severe allergic reactions occur up to this point, the second phase of desensitization is initiated.
• Maintenance phase: In the second phase, the allergen injections with the maximum dose only take place once a month. This regular exposure to the allergen stimulates the immune system to develop a habituation. During the pollen season, the therapy can possibly be interrupted or the allergen dose reduced so that the patient’s immune system is not overburdened.

Since this is a long-term therapy, the classic form of hyposensitization requires patience and consistency. Regular visits to the doctor are urgently needed in order to be able to carry out the hyposensitization successfully. Even therapeutic successes cannot necessarily be recognized immediately. However, if there is still no improvement after two years, for example due to the absence of symptoms or a lower need for medication, a decision should be made with the doctor whether the therapy should be discontinued prematurely.
Note: In the case of allergies to insect venom, it may be necessary to carry out the desensitization over a period of five years.

If allergies lead to very severe reactions, which is often the case with insect venom allergies, short-term therapy, known as rush immunotherapy , is recommended. In this way, the risk of an allergic reaction is minimized in the shortest possible time. The patient is given allergen injections about every 30 to 60 minutes for immunization over a period of two or three days. This form of therapy carries a significantly higher risk of side effects than conventional hyposensitization. For this reason and because of the high frequency of injections, rush immunotherapy takes place under supervision in a clinic.
Note:Although the acute treatment shows much faster results than conventional hyposensitization, the rush therapy must be repeated at least three times at intervals of one year. The total duration of the immunization is therefore three years for this variant as well.

A relatively new variant of hyposensitization is sublingual immunotherapy . In this case, the allergen is not injected under the skin, but taken orally once a day in the form of drops or tablets that melt under the tongue for a while. The advantage of this method is that the patient can take the preparation at home and does not have to go to the doctor’s office every time. Only the first intake usually takes place in the presence of the doctor to ensure that no complications arise. So far, however, this type of therapy has only been successful for hay fever patients.

Does hyposensitization have side effects?

As with vaccinations, side effects can also occur when performing hyposensitization. These usually manifest themselves with symptoms that also occur with normal allergic reactions. When taken orally, itching in the mouth and throat, swollen mucous membranes or gastrointestinal problems are possible. After injections, local itching, redness or swelling around the injection site may occur. Sometimes there are stronger reactions like hives or asthma. In rare cases, anaphylactic shockdevelop. It is therefore highly advisable to stay in the doctor’s office for about half an hour after an injection so that any complications can be treated quickly. In addition, the benefits of treatment should always be weighed against the risks.