Allergies to insect bites

Allergy to insect bites: From local reaction to anaphylaxis

The reaction to an insect bite occurs in everyone, but it is important to distinguish a normal local reaction, a large local reaction, and a life‑threatening systemic allergic reaction. The bite of any insect can cause redness and itching. However, true allergy is most often caused by the venom of hymenopteran insects: bees, wasps, hornets and ants.

What causes the allergy: Venom, not the bite

Unlike mosquitoes, which inject saliva, hymenopteran insects inject venom that contains powerful protein allergens. The immune system of a person with allergy produces IgE antibodies to these proteins. Upon a subsequent bite, a massive release of histamine occurs, which triggers an allergic reaction.

Types of reactions to a bite

• Normal local reaction: Pain, redness and swelling up to a few centimeters in diameter around the bite site. This is not an allergy, but a normal toxic effect of the venom.
• Large local reaction: Swelling significantly larger, may spread over the entire limb (for example, from the hand to the elbow). Although it looks frightening, it is usually not life‑threatening unless the swelling is in the neck area.
• Systemic allergic reaction (anaphylaxis): The most dangerous type. The reaction affects the whole body. Symptoms develop quickly, within a few minutes, and may include:
  • Hives over the entire body, intense itching.
  • Swelling of the lips, tongue, throat, leading to difficulty breathing and wheezing.
  • Abdominal pain, nausea, vomiting.
  • Dizziness, drop in blood pressure, loss of consciousness.

A systemic reaction to an insect bite is a medical emergency that requires immediate administration of epinephrine. Information about typical reactions in children can be read on the page "Insect bites in children".