Scit

Acronym for "specific subcutaneous immunotherapy". Repeated subcutaneous application of one or more clinically relevant allergen extracts in increasing concentrations until a so-called maintenance dose is reached. The aim of this immunomodulating therapy is the induction of an immune tolerance of the body on the humoral and cellular level against type I allergens (allergic reaction of the immediate type) under standardized conditions.

The indication for specific subcutaneous immunotherapy must be strictly defined. Immunotherapy (insect venom hyposensitization) against bee and/or wasp is the form of specific immunotherapy that has been shown to have the best results. See also immunotherapy, specific.

The therapy is carried out depending on the clinical symptoms.

Short anamnesis before (!) each injection: Tolerance of the last injection, allergic reactions since last treatment (e.g. insect bite), general condition (infections, asthmatic complaints, overexertion), if necessary postponement of the injection with subsequent reduction of the dose. For asthmatics: peak flow measurement; control of the injection interval; in control examinations dose reduction necessary if considerable NW or interval exceeding.

S.u. immunotherapy, specific.

According to the guideline, pregnancy is a contraindication for the beginning of SCIT.

A continuation of SCIT in case of life-threatening allergy (bee, wasp) and good tolerance is advisable. In the case of aeroallergens, continuation of SCIT at a reduced dose (e.g. 1/10 of the previous dose).

• Injection technique: The injection site is usually the dorsal upper arm at the middle to distal third of the arm. The injection is made subcutaneously in the middle of the fatty tissue. Lift the skin above the muscle to prevent injection into the muscle. Strictly extravasal injection under repeated aspiration with a tuberculin syringe (no air bubbles!) and thin cannula (14 to 18 mm cannula). If necessary, distribute the dose to both upper arms or apply the dose successively (application of 1/2 dose twice at 30-minute intervals). Apply a tourniquet proximally to the injection site for at least 30 minutes to reduce the outflow in case of systemic reactions. Changing the arm with each injection is often practiced, but is not obligatory.
• Accompanying measures: Cooling compress! By prophylactic premedication with antihistamines, e.g. Levocetirizine (Xusal) 1-2 Tbl. p.o. or Desloratadine (Aerius) 1-2 Tbl. p.o. the injection-related side effect rate can be reduced (e.g. 7% to 0.6% for bee venom and 0.3% for wasp venom). However, since cutaneous NW are possible indicators of the risk of respiratory and cardiovascular NW, prophylactic antihistamine administration is generally not recommended.
• Follow-up: The patient must remain in the practice/outpatient clinic for at least 30 minutes after the injection and should not make any heavy physical exertion on the same day.

In case of increased local reaction (40-65% of patients, > 10 cm, persisting for 12 hours): treatment with moist compresses, cold compresses, potent topical glucocorticoids and systemic antihistamines such as levocetirizine (Xusal, 1-2 tbl. p.o.) or desloratadine (Aerius, 1-2 tbl. p.o.). Local reactions may occur after 20-30 minutes or later and may require a dose adjustment. Large local reactions do not allow a prediction of system reactions. There are no uniform therapy standards for this. The manufacturers themselves provide different regimens: for example ALK Scherax (excessive swelling and redness at the injection site - stage 0 according to Tryba) recommendations for adults:

• Swelling < 8 cm: repeat the last injection
• Swelling 8-12 cm: reduction by 1 step
• Swelling 12-20 cm: reduction by 2 steps
• For systemic reactions: stage-appropriate treatment of anaphylactic shock, see there.

In insect venom hyposensitization with aqueous preparations, local reactions occur in up to 40% of patients in the rush phase. Local reactions are more frequent when bee venom is used than wasp venom, especially in case of higher reactivity in the skin test for bee venom. Local reactions are also more frequent in cases of severe hypersensitivity reactions and the use of higher doses (especially between 10 and 50 μg). In the case of repeated severe systemic reactions, exclusion of concomitant sensitisations, focal infections, thyroid diseases, mastocytosis, use of medication (e.g. beta-blockers). Acute treatment according to the individual stages of anaphylactic shock. With subsequent specific immunotherapy, dose reduction or use of the lowest tolerated maintenance dose, provided that it is at least 50 μg. Possible attempt to increase the long-term maintenance dose to 100 μg/4 weeks.

Remember! SCIT is the gold standard of specific immunotherapy.

Most SCIT products contain 0.5% phenol in saline solution. In one injection about 2.0- 2.5 mg are injected.

1. Wieczorek D et al (2014) Incompatibility of specific immunotherapy with hymenopteran toxin. dermatologist 65: 791-795
2. Treudler R (2010) Allergic diseases in pregnant women. dermatologist 61: 1027-1033