Specific immunotherapy (hypo- or desensitization).

Specific immunotherapy, abbreviated SIT, also called hypo- or desensitization or allergy vaccination, is so far the only therapeutic procedure for treating allergies that addresses the cause. It does not aim to relieve symptoms such as allergic rhinitis, eye itching or skin rash  but gradually accustoms the misguided immune system to the allergy trigger until it no longer overreacts to it.  

Specific immunotherapy is mainly used for an immediate-type allergic reaction and can lead to significant improvement to persistent freedom from symptoms. This process takes time, which is why the therapy usually extends over about three years. It is therefore not suitable for the treatment of acute symptoms, but can relieve the allergy in the long term.

Before starting SIT, the attending physician determines which allergens the body reacts to through various examinations and a allergy test . Specific immunotherapy can then be administered in two forms:

• Subcutaneous immunotherapy (SCIT): In this form, the doctor injects extracts containing the allergen in low doses just under the skin of the upper arm. The injections are repeated at regular intervals of four to six weeks, with the allergen dose gradually increasing in the initial phase. Once a certain maintenance dose is reached, this is maintained over the remaining period (usually 3 years) until the allergy symptoms improve.
• Sublingual Immunotherapy (SLIT): In SLIT, the allergens are administered in the form of drops or tablets which are dissolved under the tongue in the mouth and absorbed through the mucous membranes. Here, only the first intake takes place under medical supervision, the further treatment is carried out by the patient independently at home. It is important to take daily over the period of three years.

Who decides to SIT, should be aware that the success of the therapy is not immediately noticeable after the first session. Over the period of three years, several appointments are necessary to gradually weaken the sensitization of the immune system in small steps and with low doses of allergens. In most cases, patients notice a significant improvement in their allergy after one year.

By regularly administering the allergy triggers, the immune system is to be accustomed to the actually harmless substances. This results in a kind of learning process, in which the body's defenses are supposed to learn not to overreact to pollen or dust, for example.

The targeted administration of allergens, to which the body otherwise reacts with severe symptoms, can lead to complications even at very low concentrations - even if only very rarely. In order to be able to act quickly in the event of anaphylactic shock, the therapy should therefore always be carried out under medical supervision.

Also possible are side effects such as skin reactions at the injection site, e.g. redness, swelling and itching. Also may be itching in the mouth or tingling on the tongue. On the day of the injection, some patients may feel somewhat fatigued. However, the side effects usually disappear after one day.

Hyposensitization can only be performed if the allergy-causing substance is clearly known and is also only promising for immediate-type allergies (type I). contact allergies, cross allergies and intolerances cannot be treated directly by this. For people with insect-sting-allergy on the other hand, SIT can be life-saving, as a sting alone can be fatal.

For pollen allergy and house dust allergy hyposensitization also proceeds very successfully in many cases. In the case of a severe animal hair allergy or mold allergy the therapy can be carried out, but with somewhat lower chances of success.

The allergy vaccination often leads to a permanent relief of the symptoms, which in many patients after the end of the therapy even disappear completely. If your hay fever has increased more and more in recent years or new allergy triggers are constantly added, you should talk to the doctor about the possibility of specific immunotherapy. This can prevent a "floor change" in time, in which the symptoms spread to the lower respiratory tract and become allergic asthma . If, on the other hand, only mild symptoms occur due to allergen exposure, treatment with allergy medications is usually sufficient.

Before you decide to undergo hyposensitization, get detailed advice from an allergist. He or she can best tell you whether the treatment is appropriate and promising in your individual case.

According to the Allergy Information Service of the Helmholtz Zentrum München the chances of success are highest in pollen allergy, insect venom allergy and house dust allergy. The goal of hyposensitization is to reduce the allergic reaction as much as possible. In many patients, the symptoms disappear completely and remain permanently absent. In others, at least a significant alleviation of the manifestation of hay fever and co. can be observed; for further treatment, anti-allergic nasal sprays and anti-allergic eye drops will suffice.

Unfortunately, not every allergy sufferer can hope for the specific immunotherapy to combat the cause of the allergy. This is because SIT may not be an option for these underlying diseases:

• chronic diseases
• autoimmune diseases
• immune deficiency
• tumors and cancers

Furthermore, the therapy cannot be performed if the permanent use of drugs such as beta blockers or immunosuppressants is necessary.

Note for pregnant women: hyposensitization should not be started during pregnancy. If you wish to have children, it is advisable to start in advance in order to get through the pregnancy without allergies.