Insect venom allergy

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In contrast to the other insects, the stinger of a honey bee has tiny barbs. As a result, the entire lancing device in the elastic human skin, including the poison bubble, is torn out of the insect's abdomen. A muscle controlled by a nerve node then pumps the entire contents of the bladder into the stab wound.

An insect venom allergy (also Hymenoptera venom allergy ) is an allergic reaction to insect venom . These occur mainly after stings by honeybees (Apis mellifera), wasps (especially Vespula vulgaris, Vespula germanica), and more rarely hornets (Vespa crabro) and bumblebees (Bombus spp.). These insects have developed a special defense strategy in which only the females inject a species-specific mixture of toxins under the skin with a venomous sting . Historically, the sting was initially a laying tube used by female insects to lay eggs , only later was it used as a defense weapon by coupling to poison glands. The sting now only serves as a weapon in workers, i.e. sterile females of state-forming insects.

There are also ant species that can sting, such as the great knot ant . In rare cases, such a sting can also trigger an allergic reaction.

Allergens

  • Bee venom currently contains 13 known individual allergens as a total extract. In addition to the major allergen phospholipase A (Api m 1), mellitin (Api m 4), which represents the main component of the poison's dry weight, as well as a hyaluronidase (Api m 2), an acid phosphatase (Api m 3) and icarapine (Api m 10) identified as important components.
  • Wasp venom has hyaluronidase, phospholipase A and wasp-specific phospholipase B as the main allergens .

Since part of the allergen spectrum between bees and wasps overlaps, allergic reactions can be triggered at the same time in individual allergy sufferers, both after bee stings and wasp stings. The allergen spectrum of hornets largely corresponds to that of wasps.

While genetic readiness ( atopy ) is required to develop a sensitization to pollen , animal hair or house dust mites , this precondition is not necessary for acquiring an insect venom allergy . In the case of insect poisons, the path to sensitization is by bypassing the immune system in the skin (and mucous membrane) ( injection allergen ).

Severity levels of anaphylaxis

The clinical picture as a result of the poison released by an insect bite leads to painful reddening and swelling at the bite site in non-allergy sufferers, which are usually less than 10 cm in diameter and subside within a day. In addition, there may be an increased local reaction ("large local reaction") in which an erythematous swelling occurs that lasts longer than 24 hours, is usually extremely painful and can be accompanied by mild general complaints such as feeling sick or shivering. Insect venom allergies show up through the occurrence of systemic reactions (general reactions). These are characterized by symptoms that have no local connection with the stab site and can be potentially life-threatening, as they are the main triggers of so-called anaphylactic reactions in adults . This is divided into four degrees of severity:

An anaphylaxis patient does not necessarily have to go through all stages I-IV.

In Germany, up to 3.5% of the population react with systemic reactions to an insect bite , up to 25% have increased local reactions (swelling larger than 10 cm in diameter for longer than 24 hours). Wasp stings in particular are the most frequently reported causes of severe anaphylaxis among adults in German-speaking countries. Every year the Federal Statistical Office records around 20 deaths from bee, wasp or hornet stings; in Switzerland, mortality in relation to the population is around twice as high.

diagnosis

The diagnosis is based on three important pillars, which can be expanded if necessary: anamnesis , skin tests and determination of antibodies in the blood. The skin tests and the antibody determination are carried out for a reliable diagnosis in the first week and repeatedly four to six weeks after the bite. If it is not possible to determine it twice, an examination two weeks after the stinging event is recommended. The aim of the diagnosis is initially the clinical classification of the severity of the sting reaction (severity I-IV). General reactions are triggered by IgE antibodies in the allergic patient that are directed against components of the insect venom. Correspondingly, diagnostics aim to detect these specific antibodies in the blood serum in order to prove allergic insect venom sensitization. The allergy sufferer's individual risk of anaphylaxis is also recorded.

algorithm

The diagnosis of an insect venom allergy and consequently the indication for specific immunotherapy with bee or wasp venom is based on a defined scheme, which is shown in simplified form below:

  1. First of all, the anamnesis of an anaphylactic reaction, ie a reaction exceeding local symptoms , must be taken
  2. Skin test for insect venom and antibody determination as part of a conventional blood sample. The specific antibodies against total bee and total wasp venom are determined
    If the evaluation of the blood values ​​agree with the anamnestically suspected insect that was responsible for the anaphylaxis, the diagnosis of the corresponding insect venom allergy is made and the patient is to be given specific immunotherapy.
    Further diagnostic steps arise if this cannot be clearly clarified: This occurs if
    • the evaluation of the blood values ​​do not match the anamnesis (e.g. the alleged insect that caused the anaphylaxis identified as a bee, but negative antibody values ​​against total bee venom and / or positive values ​​against total wasp venom)
    • Antibodies to total bee and wasp venom are positive, but it cannot be remembered that stings from both insects provoked an anaphylactic reaction. Should it be the case that anaphylactic reactions can be remembered to both insect bites, further diagnostics are urgently necessary and specific immunotherapy for both insect venom is indicated.
  3. Repetition of the skin test and determination of the specific antibodies against allergen components (bee: Api m 1; wasp: Ves v 1 and Ves v 5) that are present in the bee and wasp venom. The determination of the sensitization to individual allergen components enables an almost certain identification of the insect venom allergy, so that the patient can be given adequate immunotherapy in the event of previous uncertainties.
  4. In a final step, a basophil activation test (BAT) can be added if the diagnostic uncertainty persists. This tests the reactivity of basophilic granulocytes to allergen stimuli at the cellular level .

anamnese

Questioning the patient is a valuable basis for any diagnosis. Questions are asked about the number, symptoms and course of the sting reaction, the circumstances of the events and the type of insect. Knowing the length of time between the sting and the reaction or the symptoms enables the diagnosis or exclusion of anaphylaxis. Skin symptoms are typical in anaphylaxis, often starting with itching on the palms of the hands, soles of the feet, scalp and in the genital area, but not obligatory. These initial symptoms are often unrecognizable, especially in severe reactions with loss of consciousness. Exclusively subjective complaints such as anxiety, palpitations, and a feeling of weakness speak against anaphylaxis , but do not exclude it. The individual risk of anaphylaxis is assessed because there is a higher risk for patients if they have increased exposure to insects (due to beekeeping, a job e.g. as a fruit or bakery seller, forest worker, gardener, farmer, truck driver, or as a result of intensive exercise of outdoor activities). The risk of severe anaphylaxis is also increased if a severity III or IV reaction has occurred in the past, as well as in patients from around the age of 40, with cardiovascular diseases, with bronchial asthma , with the use of certain medications ( e.g. beta blockers , ACE- Inhibitors ), in physical or psychological stressful situations or increased basal serum tryptase concentrations, especially in the context of mastocytosis .

Skin tests

Skin tests are carried out with various insect venom (e.g. bee and wasp venom) and positive ( histamine ) and negative controls ( isotonic saline solution ) available as drugs . This is done as part of a prick test or an intracutaneous test in various poison concentrations.

Specific IgE antibodies in the serum

Specific IgE antibodies are responsible for the manifestation of an anaphylactic reaction. These antibodies are determined in the patient's serum as part of a conventional venous blood sample . Often, patients affected by an anaphylactic reaction cannot accurately identify the suspected insect. As a result of the interpretation of the patient's individual sensitization profile, the antibody determination enables the insect causing the disease to be identified. In this way, the patient can safely be given the therapy that is suitable for him, so that future insect bites can be survived without life-threatening consequences.

therapy

Since insect venom allergies can be potentially life-threatening, it is important that all sting reactions in which other reactions (such as shortness of breath, abdominal discomfort, dizziness, circulatory problems or even loss of consciousness) have occurred in addition to a swelling the size of a palm, are clarified by an allergist .

Immediately and quickly remove any stuck on the spot that may have got stuck. The spines should not be pressed together with your fingers. This would provoke a squeezing out of the poisonous sac with consequent further injection of the insecticide. Therefore, the optimal removal is done by scratching away with a fingernail.

Local reaction

The local reaction is treated topically (locally in the form of a cream or gel) with a highly effective glucocorticoid . A cooling, moist compress helps to provide adjuvant relief from the inflammatory reaction . In addition, an antihistamine is taken orally in the form of a tablet . If the local reaction is increased, short-term systemic glucocorticoid therapy may be indicated.

Systemic response

Patients with systemic reactions to an insect bite urgently require long-term care. This is based on three essential components: avoidance of allergens, self-help measures of the patient in the event of a new bite and desensitization .

Allergen avoidance

Measures to avoid a Hymenoptera sting include: a .: Avoid eating food or drinks in the open air, washing hands and mouths after eating, clothing that is largely covering, do not walk barefoot, do not wear open shoes, close-fitting clothing when riding a motorcycle and bicycle helmets with a mesh. It is advisable to be very careful, especially on days with muggy weather, as insects are particularly aggressive then. Light-colored items of clothing are preferable to dark ones, apartment windows should be closed during the day or secured with insect nets. No light in the evening when the window is open because hornets are nocturnal and light sources fly towards them. You also expose yourself to an increased risk of being bitten when picking fruit or flowers, near waste baskets and when using perfumed cosmetics. If an insect approaches, hasty or even hitting movements should be avoided. Instead, there should be a quiet retreat with slow movements. Chemical insect repellants , however, offer no protection!

Self-help measures

For self-treatment in the event of a new sting, the patient receives a so-called "emergency kit" which includes the following medication:

The timing of the application takes place in the order listed above: the antihistamine and the glucocorticoid are taken immediately after the bite. Adrenaline is only administered via an autoinjector if systemic symptoms that go beyond skin reactions occur (e.g. shortness of breath , dizziness, nausea ). In Switzerland, however, it is advisable to administer adrenaline intramuscularly in the event of a generalized skin reaction. In general, medical help must be sought immediately.

Desensitization

The treatment of an insect venom allergy is carried out through specific immunotherapy, also known as desensitization . It usually takes three to five years and shows very good response rates of around 90% protection. In the presence of an insect venom allergy, particularly endangered or particularly worried allergy sufferers should also consider “rapid desensitization”, in which the therapeutic goal can be achieved within a few days to weeks. Such a therapy must be carried out by experienced allergists in a clinic due to the significantly increased therapy risk, so that specialists can intervene immediately and optimally in the event of an anaphylactic reaction. According to the recommendations of the EAACI (European Academy of Allergy and Clinical Immunology), the indication for desensitization in adults is :

  • Patients who have had a Grade II reaction to an insect bite and
  • Patients with individual risk factors or impaired quality of life due to insect venom allergy from a grade I reaction.

Proof of a specific sensitization (specific IgE in the serum, skin test) to the poison causing the reaction is essential for the hyposensitization.

Beekeepers can be regarded as a “natural model” of desensitization : they too acquire a specific tolerance to bee venom through regular bee stings that are received at short intervals . However, even with them, a spontaneous, allergic reaction cannot be ruled out.

See also

literature

Web links

Individual evidence

  1. ↑ Ant Wiki: Article about the large knot ant ('' Manica_rubida ''). Ameisenwiki.de, accessed on July 3, 2010 .
  2. ↑ JD Seebach, C. Bucher, M. Anliker, P. Schmid-Grendelmeier, B. Wüthrich: Ant poison: a rare cause of allergic reactions in Switzerland. In: Switzerland Med Wochenschr. Volume 130, 2000, pp. 1805-1813.
  3. ^ J. Ring, K. Messmer: Incidence and severity of anaphylactoid reactions to colloid volume substitutes. In: Lancet. 1977, pp. 466-469.
  4. ^ S2k guideline for bee and wasp venom allergy, diagnosis and therapy of the German Society for Allergology and Clinical Immunology (DGAKI). In: AWMF online. (Status 2011), p. 321.