It is better for bees, wasps or hornets not to get in the way, but sometimes an unwanted meeting ends up with a painful bite. Its consequences are mostly harmless. However, in people allergic to insect venom, life-threatening reactions can occur. How do you recognize symptoms and where to seek help?
Data on the frequency of allergy to insect venom are very incomplete and are based only on approximate calculations. The main culprits causing life-threatening anaphylactic reactions are hymenoptera insects, represented in Poland by bees, wasps, bumblebees and hornets. The most commonly diagnosed allergies concern allergy to bee venom and wasp venom. The prevalence of allergy in the general population is estimated at several percent (approx. 2%). The incidence of anaphylactic reactions per bite ranges from 0,3% to 3%. In the United States, this translates to 40-100 deaths per year from hymenoptera bites. And while these are relatively small numbers, insect venom allergy is among the top three causes of fatal anaphylactic reactions (along with drug and food anaphylactic reactions).
Allergic reactions can take many forms and severity. In the most common – the so-called type I allergic reactions – IgE antibodies are responsible for their occurrence. They are produced when the body first comes into contact with an allergen. Once produced by the cells of the immune system, IgE antibodies are deposited on the membrane of white blood cells, the so-called basophils (basophils) and the so-called mast cells (mast cells). When an antigen is re-exposed to an antigen and it combines with an antibody directed against it, it causes a sudden destruction of the cell. It then releases the chemicals contained inside (including mainly histamine), which trigger an allergic reaction. Anaphylactic reaction is the type of the most severe allergic reaction in which, due to the activation of cells of the immune system (basophils and mast cells), a sudden release of large amounts of very active chemicals is triggered, causing a systemic reaction. The most severe form of anaphylactic reaction is the immediately life-threatening anaphylactic shock.
Hymenoptera bites generally cause two kinds of reactions. There are local reactions and generalized (or systemic) reactions. Local reactions are confined to the site of the sting and are usually not an allergic reaction involving IgE antibodies. They result from the toxic effects of the venom itself or the insect’s sting. It is well known to anyone who is bitten – redness, swelling, soreness and itching. These types of local reactions usually cover a few centimeters around the bite site and resolve spontaneously within 1-2 days, and cold compresses are usually sufficient to relieve symptoms. However, in about every tenth bite, the local reactions may be more severe, the swelling builds up within 2 days and may persist for up to 10 days after the bite. In addition to compresses, both steroid and non-steroidal anti-inflammatory drugs can be helpful.
The greatest concern, however, is insect bites, which give rise to generalized reactions outside the site of the bite, often involving vital, distant organs. They occur in people allergic to the venom of Hymenoptera. Allergy can occur at any age and in any person. The most susceptible are people who are exposed to frequent bites, such as beekeepers. There are over 40 different symptoms of a generalized systemic reaction that appear within minutes of being bitten. In children, skin symptoms dominate (in 60% of cases), which occur in only about 15% of adults. Skin reactions include generalized hives, swelling and redness of the skin accompanied by severe itching. If the skin reaction is accompanied by respiratory symptoms or there is a drop in blood pressure, it is called an anaphylactic reaction and requires immediate treatment. Respiratory symptoms include a feeling of breathlessness (sometimes very difficult to distinguish from rapid breathing and a feeling of lack of air due to being very nervous) due to difficulty breathing caused by increasing swelling of the larynx or bronchospasm. In the case of laryngeal edema, apart from dyspnea, there is also hoarseness, sometimes even silence, difficulty swallowing leading to drooling, and a very characteristic laryngeal wheezing called stridor. In bronchospasm, breathlessness is usually expiratory, wheezing, or an attack of sudden severe coughing. The ambulance service arriving to the patient with the use of a pulse oximeter may show reduced blood saturation, which indicates insufficient oxygenation of the blood due to the closure of the respiratory tract in the anaphylactic reaction mechanism. Cardiovascular symptoms include a drop in blood pressure resulting in an increase in heart rate, which he wants to “catch up” with his work and maintain proper blood pressure. Lowered pressure causes dizziness and, in extreme cases, even unconsciousness. A common symptom of a generalized systemic reaction are also gastrointestinal complaints, such as nausea, vomiting, abdominal pain and diarrhea.
The procedure to be followed after an insect bite depends on the severity of the symptoms. It is very important to remove the sting or venom and protect the bitten person from being bitten again. Cold compresses are usually sufficient for local reactions. Antihistamines are used in skin reactions. When there is swelling of the face, lips or tongue, it is recommended to additionally administer steroid drugs. Situations that require immediate treatment include those where laryngeal edema, bronchospasm are suspected, or there is a drop in blood pressure and loss of consciousness. An ambulance should be called immediately. The only medicine that can save the life of the bitten person is adrenaline. People allergic to insect venoms should be equipped with a ready-to-use pre-filled syringe containing the appropriate dose of adrenaline. Drugs from the remaining groups (antihistamines, glucocorticosteroids) are important as complementary treatment and are not able to replace the administration of adrenaline.
People who developed a generalized reaction after an insect sting should undergo allergological diagnosis. Its purpose is to confirm that the symptoms observed after an insect bite were of an allergic nature. For this purpose – apart from collecting a detailed interview with the patient and establishing a detailed scenario of events and symptoms that occurred after the bite – specialized tests are performed to check whether the reaction that has taken place is related to the presence of IgE antibodies directed against the venom of the suspected person. insect allergy. This can be demonstrated in two ways: either by skin testing with the venom of an insect that is suspected of causing sensitization, or by testing for IgE antibodies against the venom of the insect in the blood. The results of these tests should be interpreted with great caution and always taking into account the symptoms that occurred during the insect bite. It is known that it is possible that skin tests may be negative in people who are allergic (performed too quickly after the onset of a generalized skin reaction) and that, on the other hand, in more than 30% of the population it is possible to show the presence of specific IgE antibodies, although never they have symptoms of allergy.
If an allergy is confirmed by the tests mentioned above in a person who has experienced a systemic reaction, the person may qualify for treatment. Treatment for insect venom allergy is called “desensitization”, which is medically known as specific immunotherapy. It consists in administering insect venom in very small doses in order to develop a tolerance. Treatment takes several years and is a very effective method of preventing future life-threatening reactions. It is known that in a person who has experienced a generalized reaction, re-biting is associated with an approximately 30-60% risk of recurrence of the life-threatening reaction. Specific immunotherapy can reduce this risk to less than 5%.
Text: lek. Paulina Jurek
Also read: Anaphylactic shock – more than an allergy
Allergy? What’s all the fuss?
Insect venom allergy – how to reduce the risk?