Insect venoms

Dr. Michaël Hofer

Immunology & Allergology, Pediatrics, CHUV, Lausanne

June 28, 2022

Insect venom is a type of poison that insects use to defend themselves. When they feel threatened, they will either sting or bite any person standing nearby, causing a possible allergic reaction. Some of the well-known insects with venomous bites or stings include wasps, hornets, fire ants, and bees. Most bites or stings usually cause minor inconveniences but they could potentially be life-threatening for some. Minor reactions cause redness of the skin, swelling, itching, numbness, or tingling. On the other hand, major reactions, which require immediate medical care, could include fever, difficulty breathing, muscle spasms, nausea, swelling, confusion, or even loss of consciousness.

Would you like to know more? Read below the article by Dr. Michaël Hofer.


During the hot season, insect bites are frequent and usually only cause minor inconvenience. Many types of insects can cause allergic reactions: mosquitoes, horseflies, ants, wasps, bees…. Apart from the last two insects mentioned which are Hymenoptera and which we will discuss in detail in this chapter, insects generally only trigger localized allergic reactions. The more severe reactions are anecdotal in our latitudes. Serious reactions are most often secondary to bites from insects of the order Hymenoptera, which includes wasps, bees, hornets, and bumblebees. Hymenoptera injects venom which contains proteins that can be sensitized and that will be recognized by the immune system in the event of an allergic reaction. Since many of these venoms are cross-reactive, diagnostic tests and specific treatments will only be done for wasp and bee venoms. A genetic predisposition for allergies, or atopy, is not necessary to develop an allergy to hymenoptera venoms. Thus, anyone can one day have an allergic reaction following a bite of a Hymenoptera. In the event of a generalized reaction, medical management is indicated, including the necessary investigations, prevention advice, an emergency kit, and desensitization depending on the severity of the reaction.


Following a bite, the insect’s venom can induce toxic effects at the site of the sting or remotely if enough venom is getting into the bloodstream. These toxic effects depend on the amount of venom injected. In the case of allergy, the intensity of the reaction is not proportional to the amount of venom and depends on the reactivity of the immune system. An allergic reaction can be localized around the site of the sting, or generalized with distant symptoms, even affecting the whole body (anaphylactic reaction). Generalized allergic reactions or anaphylaxis are classified according to their severity according to a clinical score (see chapter III, text 10: acute allergies).

Usually, the generalized reaction begins a few minutes after or within the hour after the insect bite. The reaction can affect the skin in the form of hives or angioedema (swelling, especially of the face), breathing with asthma or laryngeal obstruction, digestion with vomiting or diarrhea. The generalized reaction can also lead to a state of shock with a drop in blood pressure, loss of consciousness, and cyanosis, or generate anxiety important.

Severe reactions are usually due to the venom of hymenoptera (wasp, bee, hornet) and are often more severe after a bee sting than a wasp sting.


The diagnosis of allergy to hymenoptera venoms can be made thanks to specialized examinations. However, anamnestic information is important: severity of the allergic reaction and type of insect. These elements will help to interpret the examinations performed and to decide on the treatment. As the specialized consultation often takes place several weeks after the reaction, it would be helpful to quickly note the symptoms observed during the reaction and the type of insect, if we managed to identify him. Indeed, it is not uncommon for a patient to be sensitized with wasp and bee venom and, if the identification of the hymenoptera involved in the reaction did not been made, desensitization should be practiced against the two types of venom, which implies double injections.

In search of awareness for hymenoptera venoms, we measure allergy antibodies (IgE) specific in the blood and we can do intradermal skin tests with wasp and bee venoms. These exams can be performed at any age, especially in children, and are the domain of the specialist. The indication of desensitization will be based on the severity of the reaction and the result of diagnostic tests.


In the event of an allergy to the venom of an insect, without a bite from the insect in question, there is no allergy. It is therefore imperative to take all measures useful prevention measures (described below).

Be sure you can prevent any needle sticking is impossible, especially in children. Thus, the patient allergic to a venom insect should keep within reach in hand his emergency set, which includes an antihistamine, auto-injectable syringe adrenaline, and tablets cortisone. In the event of a bite, if it is a bee, remove immediately dart and warn someone who has been stung by an insect to which one is allergic. After the insect bite or at least as soon as the onset of the allergic reaction, take the antihistamine at the prescribed doses and have the epinephrine syringe (Epipen®) ready. In the event of a generalized allergic reaction, use an epinephrine syringe, according to the instructions (apply the ready-to-use syringe to the thigh). Do not hesitate to use the epinephrine syringe that is safe for use in a person in usual good health. If the area is isolated, take cortisone as a precaution according to the doctor’s instructions. When an allergic reaction has occurred after an insect bite, you should always consult a doctor urgently, even if the situation improves after applying emergency treatment. Indeed, adrenaline has a limited effect in time and the reaction may take over and take the life of the patient in danger. In the event of an intervention by a third party, care must be taken to position the patient, especially when transporting, and make the head lower than the lower limbs (transport on the stairs!), especially if the blood pressure is low.
Desensitization for Hymenoptera venoms has been shown to be effective in significantly reducing the risk of a severe reaction following a sting of the insect in question. Several controlled studies have shown efficacy from 78 to 100% during a new bite (local reaction only), this protection is even better for wasp venom. This treatment consists of injections subcutaneously with an increasing dose of venom until the maintenance dose is obtained (100 µg). This dose will then be repeated every month for 3 to 5 years. The sentence dose escalation should be performed by an allergist and the maintenance phase can be done by the attending physician. Children from the age of 5 can also benefit from this treatment, which will allow them to be able again normally participate in outdoor activities (excursions, school runs, etc.).
Desensitization for wasp or bee venoms is long and not devoid of risks. It will be reserved for patients who are at high risk of severe reaction upon re-exposure to the insect’s venom. Based on work that analyzed the natural evolution of allergy to hymenoptera venoms, it has been shown that patients who have presented a severe reaction are those who, are most at risk of having a severe reaction again, putting potentially their life in danger. These are the patients who should benefit from desensitization. It should be remembered that local allergic reactions after sting insects are common in the population, but severe reactions are much rarer. A patient who has extensive local reactions after the injection insect will therefore have a low risk of developing an allergic reaction severe during a subsequent bite and does not require desensitization under any circumstances.

In conclusion, allergic reactions following insect bites are frequent, but, in general, banal. In the event of a generalized reaction, taking specialized load is indicated for carrying out investigations and treatments necessary, and instruct the patient on the steps to take in the event of a new bite.


  • Avoid sudden movements. The insect will sting only if it is afraid.
  • Do not walk with bare feet (swimming pool!). Wasps and bees can be hidden in the grass.
  • Perspiration attracts insects. Be careful with the effort outside.
  • Avoid fragrant perfumes or cosmetics.
  • Be well covered in the event of a high-speed ride (motorcycle, convertible car).
  • Avoid loose clothing where an insect could enter without your knowledge.
  • Avoid leaving uncovered food outside. Avoid keeping garbage cans unclosed.
  • Do not drink from a closed container. An insect may have entered the container.
  • Do not take care of honeycombs and wasps, but call in a specialist.
  • Use a venom pump in case of bites or stings.

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