Insect bites and stings

Insect bites and stings can lead to reactions ranging from local irritation and mild swelling, through to dangerous anaphylaxis with unconsciousness and respiratory distress.

Treatment for local reactions is usually entirely supportive, aimed at alleviating discomfort and swelling. Severe reactions and anaphylaxis require immediate intervention to maintain airway patency and prevent cardiovascular collapse. Adrenaline (epinephrine) is the mainstay treatment of severe reactions, and intravenous fluids may also be needed.

Fatal spider bites are exceedingly rare. Most spider bites can be treated with supportive care.

There is a risk of late-phase (delayed) local swelling that can be significant and may show lymphangitic streaks. Anaphylactic reactions begin within 20-40 minutes in the great majority of cases, but a few reactions are delayed in onset, and there is risk of biphasic anaphylaxis following an initial anaphylactic reaction.

Primary care physicians should be notified of severe reactions involving their patients.

This topic focuses on insect bites and stings in adults.

The term 'insect' refers to a distinct taxonomic class. However, it is used generically throughout this topic to represent a multitude of bugs, including arachnids. Encounters with insects or arachnids can result in bites or stings.

Bites stem from puncture with a proboscis (head appendage) or fangs, or from chewing with mouth parts. Depending on the source, bites range from being immediately painful to completely unfelt, and health consequences may be caused by local trauma, the injection of various substances (irritants, venoms, poisons, toxins, anaesthetics, enzymes, anticoagulants), disease transmission, secondary infection, or systemic allergic reactions (rare).

Stings from insects are administered from ovipositors (organs used for laying eggs that may also inject various noxious substances) or modified ovipositors (e.g., barbed stingers of bees and wasps). Stings are almost always immediately painful. Reactions range from local irritation and swelling to life-threatening anaphylactic reactions.[Figure caption and citation for the preceding image starts]: Honeybee stinging fleshCourtesy of Rick Vetter [Citation ends].[Figure caption and citation for the preceding image starts]: Close-up of honeybee stingerCourtesy of Rick Vetter [Citation ends].